Exploring effectiveness of team communication: Balancing synchronous and asynchronous communication in design teams

NARCIS (Netherlands)

Otter, den A.F.H.J.; Emmitt, S.

2007-01-01

Purpose – Effective teams use a balance of synchronous and asynchronous communication. Team communication is dependent on the communication acts of team members and the ability of managers to facilitate, stimulate and motivate them. Team members from organizations using different information systems

A note on chaotic synchronization of time-delay secure communication systems

International Nuclear Information System (INIS)

Li Demin; Wang Zidong; Zhou Jie; Fang Jianan; Ni Jinjin

2008-01-01

In a real world, the signals are often transmitted through a hostile environment, and therefore the secure communication system has attracted considerable research interests. In this paper, the observer-based chaotic synchronization problem is studied for a class of time-delay secure communication systems. The system under consideration is subject to delayed state and nonlinear disturbances. The time-delay is allowed to be time-varying, and the nonlinearities are assumed to satisfy global Lipschitz conditions. The problem addressed is the design of a synchronization scheme such that, for the admissible time-delay as well as nonlinear disturbances, the response system can globally synchronize the driving system. An effective algebraic matrix inequality approach is developed to solve the chaotic synchronization problem. A numerical example is presented to show the effectiveness and efficiency of the proposed secure communication scheme

Synchronous Computer-Mediated Communication and Interaction

Science.gov (United States)

Ziegler, Nicole

2016-01-01

The current study reports on a meta-analysis of the relative effectiveness of interaction in synchronous computer-mediated communication (SCMC) and face-to-face (FTF) contexts. The primary studies included in the analysis were journal articles and dissertations completed between 1990 and 2012 (k = 14). Results demonstrate that interaction in SCMC…

Finite-Time Synchronization of Chaotic Systems with Different Dimension and Secure Communication

Directory of Open Access Journals (Sweden)

Shouquan Pang

2016-01-01

Full Text Available Finite-time synchronization of chaotic systems with different dimension and secure communication is investigated. It is rigorously proven that global finite-time synchronization can be achieved between three-dimension Lorenz chaotic system and four-dimension Lorenz hyperchaotic system which have certain parameters or uncertain parameters. The electronic circuits of finite-time synchronization using Multisim 12 are designed to verify our conclusion. And the application to the secure communications is also analyzed and discussed.

Detection and Symbol Synchronization for Multiple-bit Per Photon Optical Communications

Science.gov (United States)

Marshall, W. K.

1985-01-01

Methods of detection and synchronization in a highly efficient direct detection optical communication system are reported. Results of measurements on this moderate-rate demonstration system capable of transmitting 2.5 bits/detected photon in low-background situations indicate that symbol slot synchronization is not a problem, and that a simple symbol detection scheme is adequate for this situation. This system is a candidate for interplanetary optical communications.

Communication with spatial periodic chaos synchronization

International Nuclear Information System (INIS)

Zhou, J.; Huang, H.B.; Qi, G.X.; Yang, P.; Xie, X.

2005-01-01

Based on the spatial periodic chaos synchronization in coupled ring and linear arrays, we proposed a random high-dimensional chaotic encryption scheme. The transmitter can choose hyperchaotic signals randomly from the ring at any different time and simultaneously transmit the information of chaotic oscillators in the ring to receiver through public channel, so that the message can be masked by different hyperchaotic signals in different time intervals during communication, and the receiver can decode the message based on chaos synchronization but the attacker does not know the random hyperchaotic dynamics and cannot decode the message. Furthermore, the high sensitivity to the symmetry of the coupling structure makes the attacker very difficult to obtain any useful message from the channel

Symbol Synchronization for Diffusion-Based Molecular Communications.

Science.gov (United States)

Jamali, Vahid; Ahmadzadeh, Arman; Schober, Robert

2017-12-01

Symbol synchronization refers to the estimation of the start of a symbol interval and is needed for reliable detection. In this paper, we develop several symbol synchronization schemes for molecular communication (MC) systems where we consider some practical challenges, which have not been addressed in the literature yet. In particular, we take into account that in MC systems, the transmitter may not be equipped with an internal clock and may not be able to emit molecules with a fixed release frequency. Such restrictions hold for practical nanotransmitters, e.g., modified cells, where the lengths of the symbol intervals may vary due to the inherent randomness in the availability of food and energy for molecule generation, the process for molecule production, and the release process. To address this issue, we develop two synchronization-detection frameworks which both employ two types of molecule. In the first framework, one type of molecule is used for symbol synchronization and the other one is used for data detection, whereas in the second framework, both types of molecule are used for joint symbol synchronization and data detection. For both frameworks, we first derive the optimal maximum likelihood (ML) symbol synchronization schemes as performance upper bounds. Since ML synchronization entails high complexity, for each framework, we also propose three low-complexity suboptimal schemes, namely a linear filter-based scheme, a peak observation-based scheme, and a threshold-trigger scheme, which are suitable for MC systems with limited computational capabilities. Furthermore, we study the relative complexity and the constraints associated with the proposed schemes and the impact of the insertion and deletion errors that arise due to imperfect synchronization. Our simulation results reveal the effectiveness of the proposed synchronization schemes and suggest that the end-to-end performance of MC systems significantly depends on the accuracy of the symbol

A Model for Content and Communication Management in Synchronous Learning

Science.gov (United States)

Raymond, David; Kazuhide, Kanenishi; Matsuura, Kenji; Baudin, Veronique; Gayraud, Thierry; Yano, Yoneo; Diaz, Michel

2005-01-01

Asynchronous web-based learning environments are not usually as interactive or adaptive compared to traditional classrooms. The use of synchronous communication tools may be a solution to recreating the link between students and professors. However, synchronous collaborative learning environments are often restricted to a set of communication…

An adaptive chaos synchronization scheme applied to secure communication

International Nuclear Information System (INIS)

Feki, Moez

2003-01-01

This paper deals with the problem of synchronization of a class of continuous-time chaotic systems using the drive-response concept. An adaptive observer-based response system is designed to synchronize with a given chaotic drive system whose dynamical model is subjected to unknown parameters. Using the Lyapunov stability theory an adaptation law is derived to estimate the unknown parameters. We show that synchronization is achieved asymptotically. The approach is next applied to chaos-based secure communication. To demonstrate the efficiency of the proposed scheme numerical simulations are presented

Improving Communicative Competence through Synchronous Communication in Computer-Supported Collaborative Learning Environments: A Systematic Review

Science.gov (United States)

Huang, Xi

2018-01-01

Computer-supported collaborative learning facilitates the extension of second language acquisition into social practice. Studies on its achievement effects speak directly to the pedagogical notion of treating communicative practice in synchronous computer-mediated communication (SCMC): real-time communication that takes place between human beings…

Current Trend Towards Using Soft Computing Approaches to Phase Synchronization in Communication Systems

Science.gov (United States)

Drake, Jeffrey T.; Prasad, Nadipuram R.

1999-01-01

This paper surveys recent advances in communications that utilize soft computing approaches to phase synchronization. Soft computing, as opposed to hard computing, is a collection of complementary methodologies that act in producing the most desirable control, decision, or estimation strategies. Recently, the communications area has explored the use of the principal constituents of soft computing, namely, fuzzy logic, neural networks, and genetic algorithms, for modeling, control, and most recently for the estimation of phase in phase-coherent communications. If the receiver in a digital communications system is phase-coherent, as is often the case, phase synchronization is required. Synchronization thus requires estimation and/or control at the receiver of an unknown or random phase offset.

State estimation and synchronization of pendula systems over digital communication channels

Science.gov (United States)

Fradkov, A. L.; Andrievsky, B.; Ananyevskiy, M.

2014-04-01

The recent results on nonlinear systems synchronization and control under communication constraints are applied to the remote state estimation and synchronization for a class of exogenously excited nonlinear Lurie systems. State estimation of the chain of diffusively coupled pendulums over the digital communication channel with limited capacity is experimentally studied. Advantage of the adaptive coding procedure under the conditions of the plant model uncertainty and irregular disturbances is shown. Quality of the estimation is evaluated by means of the experiments with the multi-pendulum set-up. Experimental study of master-slave synchronization over network (local network, wireless network) for the system with two cart-pendulums is presented.

Fast Burst Synchronization for Power Line Communication Systems

Directory of Open Access Journals (Sweden)

Lampe Lutz

2007-01-01

Full Text Available Fast burst synchronization is an important requirement in asynchronous communication networks, where devices transmit short data packets in an unscheduled fashion. Such a synchronization is typically achieved by means of a preamble sent in front of the data packet. In this paper, we study fast burst synchronization for power line communication (PLC systems operating below 500 kHz and transmitting data rates of up to about 500 kbps as it is typical in various PLC network applications. In particular, we are concerned with the receiver processing of the preamble signal and the actual design of preambles suitable for fast burst synchronization in such PLC systems. Our approach is comprehensive in that it takes into account the most distinctive characteristics of the power line channel, which are multipath propagation, highly varying path loss, and disturbance by impulse noise, as well as important practical constraints, especially the need for spectral shaping of the preamble signal and fast adjustment of the automatic gain control (AGC. In fact, we regard the explicit incorporation of these various requirements into the preamble design as the main contribution of this work. We devise an optimization criterion and a stochastic algorithm to search for suitable preamble sequences. A comprehensive performance comparison of a designed and two conventional preambles shows that the designed sequence is superior in terms of (a fast burst synchronization in various transmission environments, (b fast AGC adjustment, and (c compliance of its spectrum with the spectral mask applied to the data transmit signal.

Hybrid electronic/optical synchronized chaos communication system.

Science.gov (United States)

Toomey, J P; Kane, D M; Davidović, A; Huntington, E H

2009-04-27

A hybrid electronic/optical system for synchronizing a chaotic receiver to a chaotic transmitter has been demonstrated. The chaotic signal is generated electronically and injected, in addition to a constant bias current, to a semiconductor laser to produce an optical carrier for transmission. The optical chaotic carrier is photodetected to regenerate an electronic signal for synchronization in a matched electronic receiver The system has been successfully used for the transmission and recovery of a chaos masked message that is added to the chaotic optical carrier. Past demonstrations of synchronized chaos based, secure communication systems have used either an electronic chaotic carrier or an optical chaotic carrier (such as the chaotic output of various nonlinear laser systems). This is the first electronic/optical hybrid system to be demonstrated. We call this generation of a chaotic optical carrier by electronic injection.

Exponential networked synchronization of master-slave chaotic systems with time-varying communication topologies

International Nuclear Information System (INIS)

Yang Dong-Sheng; Liu Zhen-Wei; Liu Zhao-Bing; Zhao Yan

2012-01-01

The networked synchronization problem of a class of master-slave chaotic systems with time-varying communication topologies is investigated in this paper. Based on algebraic graph theory and matrix theory, a simple linear state feedback controller is designed to synchronize the master chaotic system and the slave chaotic systems with a time-varying communication topology connection. The exponential stability of the closed-loop networked synchronization error system is guaranteed by applying Lyapunov stability theory. The derived novel criteria are in the form of linear matrix inequalities (LMIs), which are easy to examine and tremendously reduce the computation burden from the feedback matrices. This paper provides an alternative networked secure communication scheme which can be extended conveniently. An illustrative example is given to demonstrate the effectiveness of the proposed networked synchronization method. (general)

Synchronization of discrete-time hyperchaotic systems: An application in communications

International Nuclear Information System (INIS)

Aguilar-Bustos, A.Y.; Cruz-Hernandez, C.

2009-01-01

In this paper, the synchronization problem of discrete-time complex dynamics is presented. In particular, we use the model-matching approach from nonlinear control theory to synchronize two unidirectionally coupled discrete-time hyperchaotic systems. A potential application to secure/private communication of confidential information is also given. By using different (hyperchaotic) encryption schemes with a single and two transmission channels, we show that output synchronization of hyperchaotic maps is indeed suitable for encryption, transmission, and decryption of information.

Synchronization of a unified chaotic system and the application in secure communication

International Nuclear Information System (INIS)

Lu Junan; Wu Xiaoqun; Lue Jinhu

2002-01-01

This Letter further investigates the synchronization of a unified chaotic system via different methods. Several sufficient theorems for the synchronization of the unified chaotic system are deduced. A scheme of secure communication based on the synchronization of the unified chaotic system is presented. Numerical simulation shows its feasibility

Improving Communicative Competence through Synchronous Communication in Computer-Supported Collaborative Learning Environments: A Systematic Review

Directory of Open Access Journals (Sweden)

Xi Huang

2018-01-01

Full Text Available Computer-supported collaborative learning facilitates the extension of second language acquisition into social practice. Studies on its achievement effects speak directly to the pedagogical notion of treating communicative practice in synchronous computer-mediated communication (SCMC: real-time communication that takes place between human beings via the instrumentality of computers in forms of text, audio and video communication, such as live chat and chatrooms as socially-oriented meaning construction. This review begins by considering the adoption of social interactionist views to identify key paradigms and supportive principles of computer-supported collaborative learning. A special focus on two components of communicative competence is then presented to explore interactional variables in synchronous computer-mediated communication along with a review of research. There follows a discussion on a synthesis of interactional variables in negotiated interaction and co-construction of knowledge from psycholinguistic and social cohesion perspectives. This review reveals both possibilities and disparities of language socialization in promoting intersubjective learning and diversifying the salient use of interactively creative language in computer-supported collaborative learning environments in service of communicative competence.

Exploring effectiveness of team communication: Balancing synchronous and asynchronous communication in design teams

DEFF Research Database (Denmark)

den Otter, Ad; Emmitt, Stephen

2007-01-01

Effective teams use a balance of synchronous and asynchronous communication. Team communication is dependent on the communication acts of team members and the ability of managers to facilitate, stimulate and motivate them. Team members from organizations using different information systems tend...... to have different understanding, opinions, and rates of adoption and skills levels regarding specific IT tools. The purpose of this paper is to explore the effective use of tools for communication in design teams and the strategies for the use of specific tools....

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

Science.gov (United States)

Jos, Sujit; Kumar, Preetam; Chakrabarti, Saswat

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

Generalized projective synchronization via the state observer and its application in secure communication

International Nuclear Information System (INIS)

Wu Di; Li Juan-Juan

2010-01-01

Based on the improved state observer and the pole placement technique, by adding a constant which extends the scope of use of the original system, a new design method of generalized projective synchronization is proposed. With this method, by changing the projective synchronization scale factor, one can achieve not only complete synchronization, but also anti-synchronization, as well as arbitrary percentage of projective synchronization, so that the system may attain arbitrary synchronization in a relatively short period of time, which makes this study more meaningful. By numerical simulation, and choosing appropriate scale factor, the results of repeated experiments verify that this method is highly effective and satisfactory. Finally, based on this method and the relevant feedback concept, a novel secure communication project is designed. Numerical simulation verifies that this secure communication project is very valid, and moreover, the experimental result has been greatly improved in decryption time. (general)

Synchronization of spatiotemporal chaotic systems and application to secure communication of digital image

International Nuclear Information System (INIS)

Wang Xing-Yuan; Zhang Na; Ren Xiao-Li; Zhang Yong-Lei

2011-01-01

Coupled map lattices (CMLs) are taken as examples to study the synchronization of spatiotemporal chaotic systems. In this paper, we use the nonlinear coupled method to implement the synchronization of two coupled map lattices. Through the appropriate separation of the linear term from the nonlinear term of the spatiotemporal chaotic system, we set the nonlinear term as the coupling function and then we can achieve the synchronization of two coupled map lattices. After that, we implement the secure communication of digital image using this synchronization method. Then, the discrete characteristics of the nonlinear coupling spatiotemporal chaos are applied to the discrete pixel of the digital image. After the synchronization of both the communication parties, the receiver can decrypt the original image. Numerical simulations show the effectiveness and the feasibility of the proposed program. (general)

Synchronization and bidirectional communication without delay line using strong mutually coupled semiconductor lasers

Science.gov (United States)

Li, Guang-Hui; Wang, An-Bang; Feng, Ye; Wang, Yang

2010-07-01

This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers' outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides (±6%), the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication.

Synchronization and bidirectional communication without delay line using strong mutually coupled semiconductor lasers

International Nuclear Information System (INIS)

Guang-Hui, Li; An-Bang, Wang; Ye, Feng; Yang, Wang

2010-01-01

This paper numerically demonstrates synchronization and bidirectional communication without delay line by using two semiconductor lasers with strong mutual injection in a face-to-face configuration. These results show that both of the two lasers' outputs synchronize with their input chaotic carriers. In addition, simulations demonstrate that this kind of synchronization can be used to realize bidirectional communications without delay line. Further studies indicate that within a small deviation in message amplitudes of two sides (±6%), the message can be extracted with signal-noise-ratio more than 10 dB; and the signal-noise-ratio is extremely sensitive to the message rates mismatch of two sides, which may be used as a key of bidirectional communication. (general)

On eliminating synchronous communication in molecular simulations to improve scalability

Science.gov (United States)

Straatsma, T. P.; Chavarría-Miranda, Daniel G.

2013-12-01

Molecular dynamics simulation, as a complementary tool to experimentation, has become an important methodology for the understanding and design of molecular systems as it provides access to properties that are difficult, impossible or prohibitively expensive to obtain experimentally. Many of the available software packages have been parallelized to take advantage of modern massively concurrent processing resources. The challenge in achieving parallel efficiency is commonly attributed to the fact that molecular dynamics algorithms are communication intensive. This paper illustrates how an appropriately chosen data distribution and asynchronous one-sided communication approach can be used to effectively deal with the data movement within the Global Arrays/ARMCI programming model framework. A new put_notify capability is presented here, allowing the implementation of the molecular dynamics algorithm without any explicit global or local synchronization or global data reduction operations. In addition, this push-data model is shown to very effectively allow hiding data communication behind computation. Rather than data movement or explicit global reductions, the implicit synchronization of the algorithm becomes the primary challenge for scalability. Without any explicit synchronous operations, the scalability of molecular simulations is shown to depend only on the ability to evenly balance computational load.

A Dynamic Analysis of the Interplay between Asynchronous and Synchronous Communication in Online Learning: The Impact of Motivation

Science.gov (United States)

Giesbers, B.; Rienties, B.; Tempelaar, D.; Gijselaers, W.

2014-01-01

With the increased affordances of synchronous communication tools, more opportunities for online learning to resemble face-to-face settings have recently become available. However, synchronous communication does not afford as much time for reflection as asynchronous communication. Therefore, a combination of synchronous and asynchronous…

Improving Communicative Competence through Synchronous Communication in Computer-Supported Collaborative Learning Environments: A Systematic Review

OpenAIRE

Xi Huang

2018-01-01

Computer-supported collaborative learning facilitates the extension of second language acquisition into social practice. Studies on its achievement effects speak directly to the pedagogical notion of treating communicative practice in synchronous computer-mediated communication (SCMC): real-time communication that takes place between human beings via the instrumentality of computers in forms of text, audio and video communication, such as live chat and chatrooms as socially-oriented meaning c...

Survey of timing/synchronization of operating wideband digital communications networks

Science.gov (United States)

Mitchell, R. L.

1978-01-01

In order to benefit from experience gained from the synchronization of operational wideband digital networks, a survey was made of three such systems: Data Transmission Company, Western Union Telegraph Company, and the Computer Communications Group of the Trans-Canada Telephone System. The focus of the survey was on deployment and operational experience from a practical (as opposed to theoretical) viewpoint. The objective was to provide a report on the results of deployment how the systems performed, and wherein the performance differed from that predicted or intended in the design. It also attempted to determine how the various system designers would use the benefit of hindsight if they could design those same systems today.

Predictive and tempo-flexible synchronization to a visual metronome in monkeys.

Science.gov (United States)

Takeya, Ryuji; Kameda, Masashi; Patel, Aniruddh D; Tanaka, Masaki

2017-07-21

Predictive and tempo-flexible synchronization to an auditory beat is a fundamental component of human music. To date, only certain vocal learning species show this behaviour spontaneously. Prior research training macaques (vocal non-learners) to tap to an auditory or visual metronome found their movements to be largely reactive, not predictive. Does this reflect the lack of capacity for predictive synchronization in monkeys, or lack of motivation to exhibit this behaviour? To discriminate these possibilities, we trained monkeys to make synchronized eye movements to a visual metronome. We found that monkeys could generate predictive saccades synchronized to periodic visual stimuli when an immediate reward was given for every predictive movement. This behaviour generalized to novel tempi, and the monkeys could maintain the tempo internally. Furthermore, monkeys could flexibly switch from predictive to reactive saccades when a reward was given for each reactive response. In contrast, when humans were asked to make a sequence of reactive saccades to a visual metronome, they often unintentionally generated predictive movements. These results suggest that even vocal non-learners may have the capacity for predictive and tempo-flexible synchronization to a beat, but that only certain vocal learning species are intrinsically motivated to do it.

Synchronization of the chaotic secure communication system with output state delay

International Nuclear Information System (INIS)

Changchien, S.-K.; Huang, C.-K.; Nien, H.-H.; Shieh, H.-W.

2009-01-01

In this paper, we utilize a proper Lyapunov function and Lyapunov theorem, combined with LMIs method, in order to design a controller L, which ensures the synchronization between the transmission and the reception ends of the chaotic secure communication system with time-delay of output state. Meanwhile, for the purpose of increasing communication security, we encrypt and decrypt the original to-be-transmitted message with the techniques of n-shift cipher and public key. The result of simulation shows that the proposed method is able to synchronize the transmission and the reception ends of the system, and moreover, to recover the original message at the reception end. Therefore, the method proposed in this paper is effective and feasible to apply in the chaotic secure communication system.

Multiple access chaotic digital communication based on generalized synchronization

International Nuclear Information System (INIS)

Lu Junguo

2005-01-01

A novel method for multiple access chaotic digital communication based on the concept of chaos generalized synchronization and the on-line least square method is proposed. This method can be used for transmitting multiple digital information signals concurrently. We illustrate the method using a Lorenz system driving a Chua's circuit and then examine the robustness of the proposed method with respect to noise in communication channel

Collaborative Dialogue in Synchronous Computer-Mediated Communication and Face-to-Face Communication

Science.gov (United States)

Zeng, Gang

2017-01-01

Previous research has documented that collaborative dialogue promotes L2 learning in both face-to-face (F2F) and synchronous computer-mediated communication (SCMC) modalities. However, relatively little research has explored modality effects on collaborative dialogue. Thus, motivated by sociocultual theory, this study examines how F2F compares…

Synchronization of Switched Neural Networks With Communication Delays via the Event-Triggered Control.

Science.gov (United States)

Wen, Shiping; Zeng, Zhigang; Chen, Michael Z Q; Huang, Tingwen

2017-10-01

This paper addresses the issue of synchronization of switched delayed neural networks with communication delays via event-triggered control. For synchronizing coupled switched neural networks, we propose a novel event-triggered control law which could greatly reduce the number of control updates for synchronization tasks of coupled switched neural networks involving embedded microprocessors with limited on-board resources. The control signals are driven by properly defined events, which depend on the measurement errors and current-sampled states. By using a delay system method, a novel model of synchronization error system with delays is proposed with the communication delays and event-triggered control in the unified framework for coupled switched neural networks. The criteria are derived for the event-triggered synchronization analysis and control synthesis of switched neural networks via the Lyapunov-Krasovskii functional method and free weighting matrix approach. A numerical example is elaborated on to illustrate the effectiveness of the derived results.

Via generalized function projective synchronization in nonlinear Schrödinger equation for secure communication

Science.gov (United States)

Zhao, L. W.; Du, J. G.; Yin, J. L.

2018-05-01

This paper proposes a novel secured communication scheme in a chaotic system by applying generalized function projective synchronization of the nonlinear Schrödinger equation. This phenomenal approach guarantees a secured and convenient communication. Our study applied the Melnikov theorem with an active control strategy to suppress chaos in the system. The transmitted information signal is modulated into the parameter of the nonlinear Schrödinger equation in the transmitter and it is assumed that the parameter of the receiver system is unknown. Based on the Lyapunov stability theory and the adaptive control technique, the controllers are designed to make two identical nonlinear Schrödinger equation with the unknown parameter asymptotically synchronized. The numerical simulation results of our study confirmed the validity, effectiveness and the feasibility of the proposed novel synchronization method and error estimate for a secure communication. The Chaos masking signals of the information communication scheme, further guaranteed a safer and secured information communicated via this approach.

A Reusable Component for Communication and Data Synchronization in Mobile Distributed Interactive Applications

Directory of Open Access Journals (Sweden)

Abdul Malik Khan

2010-10-01

Full Text Available In Distributed Interactive Applications (DIA such as multiplayer games, where many participants are involved in a same game session and communicate through a network, they may have an inconsistent view of the virtual world because of the communication delays across the network. This issue becomes even more challenging when communicating through a cellular network while executing the DIA client on a mobile terminal. Consistency maintenance algorithms may be used to obtain a uniform view of the virtual world. These algorithms are very complex and hard to program and therefore, the implementation and the future evolution of the application logic code become difficult. To solve this problem, we propose an approach where the consistency concerns are handled separately by a distributed component called a Synchronization Medium, which is responsible for the communication management as well as the consistency maintenance. We present the detailed architecture of the Synchronization Medium and the generic interfaces it offers to DIAs. We evaluate our approach both qualitatively and quantitatively. We first demonstrate that the Synchronization Medium is a reusable component through the development of two game applications, a car racing game and a space war game. A performance evaluation then shows that the overhead introduced by the Synchronization Medium remains acceptable.

Analysis of time in establishing synchronization radio communication system with expanded spectrum conditions for communication with mobile robots

Science.gov (United States)

Latinovic, T. S.; Kalabic, S. B.; Barz, C. R.; Petrica, P. Paul; Pop-Vădean, A.

2018-01-01

This paper analyzes the influence of the Doppler Effect on the length of time to establish synchronization pseudorandom sequences in radio communications systems with an expanded spectrum. Also, this paper explores the possibility of using secure wireless communication for modular robots. Wireless communication could be used for local and global communication. We analyzed a radio communication system integrator, including the two effects of the Doppler signal on the duration of establishing synchronization of the received and locally generated pseudorandom sequence. The effects of the impact of the variability of the phase were analyzed between the said sequences and correspondence of the phases of these signals with the interval of time of acquisition of received sequences. An analysis of these impacts is essential in the transmission of signal and protection of the transfer of information in the communication systems with an expanded range (telecommunications, mobile telephony, Global Navigation Satellite System GNSS, and wireless communication). Results show that wireless communication can provide a safety approach for communication with mobile robots.

Towards a diachronic-synchronic view of future communication policies in Africa.

Science.gov (United States)

Wilson, D

1989-01-01

Democratic communication policy Africa cannot be exploited by nations that have a technological edge. Traditional, indigenous systems have to be analyzed by a diachronic-synchronic study to establish more effective communication systems for Africa. It is proposed in this diachronic- synchronic view that communication is a cultural transaction and transmission taking place over time. Old processes are synchronized with modern technology resulting in the closure of the cultural gap between traditional and modern societies. Traditional communication processes have been ignored for too long and communication as an industry has become an elite enterprise boasting expensive gadgets (television and radio, newspapers and magazines). Communication is culture, since it is a manifestation of the cultural norms of society. This monopolistic pattern of cultural or media imperialism is pervasive in the Third World. Communication theory is a multidisciplinary field which strongly reflects the music, art, religion, etc. of the society. The communication of religion has become a big cultural activity worldwide, and televangelism is a significant feature of it, although it strictly controlled in Nigeria despite the pervasiveness of religion in society. The traditional communication system consists of the village council of elders and chiefs and the gongman as a broadcaster or reporter. Modern communication systems utilize television, satellite systems, and computers. These powerful instruments, however, have become liabilities in Third World countries. Dominating powers sell these instruments of power and culture to a people who pay for the equipment by foreign loans. A very grave communication problem in Africa is the low literacy rate and the preeminence of foreign languages as the only medium for reaching majority of the literate public. The culture of the poorer nations is often distorted. Exhibition of Africa culture is rare, and Western culture is transmitted to poor nations

Social argumentation in online synchronous communication

Science.gov (United States)

Angiono, Ivan

In education, argumentation has an increasing importance because it can be used to foster learning in various fields including philosophy, history, sciences, and mathematics. Argumentation is also at the heart of scientific inquiry. Many educational technology researchers have been interested in finding out how technologies can be employed to improve students' learning of argumentation. Therefore, many computer-based tools or argumentation systems have been developed to assist students in their acquisition of argumentation skills. While the argumentation systems incorporating online debating tools present a good resource in formal settings, there is limited research revealing what argumentative skills students are portraying in informal online settings without the presence of a moderator. This dissertation investigates the nature of argumentative practices in a massively multiplayer online game where the system successfully incorporates the authentic use of online synchronous communication tools and the patterns that emerge from the interplay between a number of contextual variables including synchronicity, interest, authenticity, and topical knowledge.

Communication key using delay times in time-delayed chaos synchronization

International Nuclear Information System (INIS)

Kim, Chil-Min; Kye, Won-Ho; Rim, Sunghwan; Lee, Soo-Young

2004-01-01

We propose an efficient key scheme, which can generate a great number of communication keys, for communication using chaos synchronization. We have attained the keys from delay times of time-delay coupled chaotic systems. We explain the scheme and the efficiency by coupling Henon and logistic maps and illustrate them by coupling Navier-Stokes and Lorenz equations as a continuous system

Successive lag synchronization on dynamical networks with communication delay

International Nuclear Information System (INIS)

Zhang Xin-Jian; Wei Ai-Ju; Li Ke-Zan

2016-01-01

In this paper, successive lag synchronization (SLS) on a dynamical network with communication delay is investigated. In order to achieve SLS on the dynamical network with communication delay, we design linear feedback control and adaptive control, respectively. By using the Lyapunov function method, we obtain some sufficient conditions for global stability of SLS. To verify these results, some numerical examples are further presented. This work may find potential applications in consensus of multi-agent systems. (paper)

Time concurrency/phase-time synchronization in digital communications networks

Science.gov (United States)

Kihara, Masami; Imaoka, Atsushi

1990-01-01

Digital communications networks have the intrinsic capability of time synchronization which makes it possible for networks to supply time signals to some applications and services. A practical estimation method for the time concurrency on terrestrial networks is presented. By using this method, time concurrency capability of the Nippon Telegraph and Telephone Corporation (NTT) digital communications network is estimated to be better than 300 ns rms at an advanced level, and 20 ns rms at final level.

Security analysis of communication system based on the synchronization of different order chaotic systems

International Nuclear Information System (INIS)

Alvarez, Gonzalo; Hernandez, Luis; Munoz, Jaime; Montoya, Fausto; Li Shujun

2005-01-01

This Letter analyzes the security weakness of a recently proposed communication method based on chaotic modulation and masking using synchronization of two chaotic systems with different orders. It is shown that its application to secure communication is unsafe, because it can be broken in two different ways, by high-pass filtering and by reduced order system synchronization, without knowing neither the system parameter values nor the system key

Cryptanalyzing a discrete-time chaos synchronization secure communication system

International Nuclear Information System (INIS)

Alvarez, G.; Montoya, F.; Romera, M.; Pastor, G.

2004-01-01

This paper describes the security weakness of a recently proposed secure communication method based on discrete-time chaos synchronization. We show that the security is compromised even without precise knowledge of the chaotic system used. We also make many suggestions to improve its security in future versions

Virtually-synchronous communication based on a weak failure suspector

Science.gov (United States)

Schiper, Andre; Ricciardi, Aleta

1993-01-01

Failure detectors (or, more accurately Failure Suspectors (FS)) appear to be a fundamental service upon which to build fault-tolerant, distributed applications. This paper shows that a FS with very weak semantics (i.e., that delivers failure and recovery information in no specific order) suffices to implement virtually-synchronous communication (VSC) in an asynchronous system subject to process crash failures and network partitions. The VSC paradigm is particularly useful in asynchronous systems and greatly simplifies building fault-tolerant applications that mask failures by replicating processes. We suggest a three-component architecture to implement virtually-synchronous communication: (1) at the lowest level, the FS component; (2) on top of it, a component (2a) that defines new views; and (3) a component (2b) that reliably multicasts messages within a view. The issues covered in this paper also lead to a better understanding of the various membership service semantics proposed in recent literature.

Predicting dynamic behavior via anticipating synchronization in coupled pendulum-like systems

International Nuclear Information System (INIS)

Xu Shiyun; Yang Ying

2009-01-01

In this paper, the regime of anticipating synchronization (sometimes called predicted synchronization) in a class of nonlinear dynamical systems is investigated by testing the global asymptotical stability of time-delayed error dynamics. Sufficient conditions in terms of linear matrix inequalities are established for anticipating synchronization between such systems with and without state time delay. These results allow one to predict the dynamic behavior of the systems by using a copy of the same system that performs as a slave. Moreover, the cascaded anticipating synchronization is concerned such that several slave systems could anticipate the same master system with different delays. Concrete applications to phase-locked loops demonstrate the applicability and validity of the proposed results.

Static Deadlock Detection in MPI Synchronization Communication

OpenAIRE

Ming-Xue, Liao; Xiao-Xin, He; Zhi-Hua, Fan

2007-01-01

It is very common to use dynamic methods to detect deadlocks in MPI programs for the reason that static methods have some restrictions. To guarantee high reliability of some important MPI-based application software, a model of MPI synchronization communication is abstracted and a type of static method is devised to examine deadlocks in such modes. The model has three forms with different complexity: sequential model, single-loop model and nested-loop model. Sequential model is a base for all ...

Adaptive fuzzy observer based synchronization design and secure communications of chaotic systems

International Nuclear Information System (INIS)

Hyun, Chang-Ho; Kim, Jae-Hun; Kim, Euntai; Park, Mignon

2006-01-01

This paper proposes a synchronization design scheme based on an alternative indirect adaptive fuzzy observer and its application to secure communication of chaotic systems. It is assumed that their states are unmeasurable and their parameters are unknown. Chaotic systems and the structure of the fuzzy observer are represented by the Takagi-Sugeno fuzzy model. Using Lyapunov stability theory, an adaptive law is derived to estimate the unknown parameters and the stability of the proposed system is guaranteed. Through this process, the asymptotic synchronization of chaotic systems is achieved. The proposed observer is applied to secure communications of chaotic systems and some numerical simulation results show the validity of theoretical derivations and the performance of the proposed observer

Learning Opportunities in Synchronous Computer-Mediated Communication and Face-to-Face Interaction

Science.gov (United States)

Kim, Hye Yeong

2014-01-01

This study investigated how synchronous computer-mediated communication (SCMC) and face-to-face (F2F) oral interaction influence the way in which learners collaborate in language learning and how they solve their communicative problems. The findings suggest that output modality may affect how learners produce language, attend to linguistic forms,…

Global synchronization algorithms for the Intel iPSC/860

Science.gov (United States)

Seidel, Steven R.; Davis, Mark A.

1992-01-01

In a distributed memory multicomputer that has no global clock, global processor synchronization can only be achieved through software. Global synchronization algorithms are used in tridiagonal systems solvers, CFD codes, sequence comparison algorithms, and sorting algorithms. They are also useful for event simulation, debugging, and for solving mutual exclusion problems. For the Intel iPSC/860 in particular, global synchronization can be used to ensure the most effective use of the communication network for operations such as the shift, where each processor in a one-dimensional array or ring concurrently sends a message to its right (or left) neighbor. Three global synchronization algorithms are considered for the iPSC/860: the gysnc() primitive provided by Intel, the PICL primitive sync0(), and a new recursive doubling synchronization (RDS) algorithm. The performance of these algorithms is compared to the performance predicted by communication models of both the long and forced message protocols. Measurements of the cost of shift operations preceded by global synchronization show that the RDS algorithm always synchronizes the nodes more precisely and costs only slightly more than the other two algorithms.

Memory-based frame synchronizer. [for digital communication systems

Science.gov (United States)

Stattel, R. J.; Niswander, J. K. (Inventor)

1981-01-01

A frame synchronizer for use in digital communications systems wherein data formats can be easily and dynamically changed is described. The use of memory array elements provide increased flexibility in format selection and sync word selection in addition to real time reconfiguration ability. The frame synchronizer comprises a serial-to-parallel converter which converts a serial input data stream to a constantly changing parallel data output. This parallel data output is supplied to programmable sync word recognizers each consisting of a multiplexer and a random access memory (RAM). The multiplexer is connected to both the parallel data output and an address bus which may be connected to a microprocessor or computer for purposes of programming the sync word recognizer. The RAM is used as an associative memory or decorder and is programmed to identify a specific sync word. Additional programmable RAMs are used as counter decoders to define word bit length, frame word length, and paragraph frame length.

More Gamma More Predictions: Gamma-Synchronization as a Key Mechanism for Efficient Integration of Classical Receptive Field Inputs with Surround Predictions

Science.gov (United States)

Vinck, Martin; Bosman, Conrado A.

2016-01-01

During visual stimulation, neurons in visual cortex often exhibit rhythmic and synchronous firing in the gamma-frequency (30–90 Hz) band. Whether this phenomenon plays a functional role during visual processing is not fully clear and remains heavily debated. In this article, we explore the function of gamma-synchronization in the context of predictive and efficient coding theories. These theories hold that sensory neurons utilize the statistical regularities in the natural world in order to improve the efficiency of the neural code, and to optimize the inference of the stimulus causes of the sensory data. In visual cortex, this relies on the integration of classical receptive field (CRF) data with predictions from the surround. Here we outline two main hypotheses about gamma-synchronization in visual cortex. First, we hypothesize that the precision of gamma-synchronization reflects the extent to which CRF data can be accurately predicted by the surround. Second, we hypothesize that different cortical columns synchronize to the extent that they accurately predict each other’s CRF visual input. We argue that these two hypotheses can account for a large number of empirical observations made on the stimulus dependencies of gamma-synchronization. Furthermore, we show that they are consistent with the known laminar dependencies of gamma-synchronization and the spatial profile of intercolumnar gamma-synchronization, as well as the dependence of gamma-synchronization on experience and development. Based on our two main hypotheses, we outline two additional hypotheses. First, we hypothesize that the precision of gamma-synchronization shows, in general, a negative dependence on RF size. In support, we review evidence showing that gamma-synchronization decreases in strength along the visual hierarchy, and tends to be more prominent in species with small V1 RFs. Second, we hypothesize that gamma-synchronized network dynamics facilitate the emergence of spiking output that

Working Memory and Auditory Imagery Predict Sensorimotor Synchronization with Expressively Timed Music.

Science.gov (United States)

Colley, Ian D; Keller, Peter E; Halpern, Andrea R

2017-08-11

Sensorimotor synchronization (SMS) is prevalent and readily studied in musical settings, as most people are able to perceive and synchronize with a beat (e.g. by finger tapping). We took an individual differences approach to understanding SMS to real music characterized by expressive timing (i.e. fluctuating beat regularity). Given the dynamic nature of SMS, we hypothesized that individual differences in working memory and auditory imagery-both fluid cognitive processes-would predict SMS at two levels: 1) mean absolute asynchrony (a measure of synchronization error), and 2) anticipatory timing (i.e. predicting, rather than reacting to beat intervals). In Experiment 1, participants completed two working memory tasks, four auditory imagery tasks, and an SMS-tapping task. Hierarchical regression models were used to predict SMS performance, with results showing dissociations among imagery types in relation to mean absolute asynchrony, and evidence of a role for working memory in anticipatory timing. In Experiment 2, a new sample of participants completed an expressive timing perception task to examine the role of imagery in perception without action. Results suggest that imagery vividness is important for perceiving and control is important for synchronizing with, irregular but ecologically valid musical time series. Working memory is implicated in synchronizing by anticipating events in the series.

Adaptative synchronization in multi-output fractional-order complex dynamical networks and secure communications

Science.gov (United States)

Mata-Machuca, Juan L.; Aguilar-López, Ricardo

2018-01-01

This work deals with the adaptative synchronization of complex dynamical networks with fractional-order nodes and its application in secure communications employing chaotic parameter modulation. The complex network is composed of multiple fractional-order systems with mismatch parameters and the coupling functions are given to realize the network synchronization. We introduce a fractional algebraic synchronizability condition (FASC) and a fractional algebraic identifiability condition (FAIC) which are used to know if the synchronization and parameters estimation problems can be solved. To overcome these problems, an adaptative synchronization methodology is designed; the strategy consists in proposing multiple receiver systems which tend to follow asymptotically the uncertain transmitters systems. The coupling functions and parameters of the receiver systems are adjusted continually according to a convenient sigmoid-like adaptative controller (SLAC), until the measurable output errors converge to zero, hence, synchronization between transmitter and receivers is achieved and message signals are recovered. Indeed, the stability analysis of the synchronization error is based on the fractional Lyapunov direct method. Finally, numerical results corroborate the satisfactory performance of the proposed scheme by means of the synchronization of a complex network consisting of several fractional-order unified chaotic systems.

Synchronizing modified van der Pol-Duffing oscillators with offset terms using observer design: application to secure communications

International Nuclear Information System (INIS)

Fodjouong, G J; Fotsin, H B; Woafo, P

2007-01-01

This study addresses the adaptive synchronization of the modified van der Pol-Duffing (MVDPD) oscillator with offset terms. From our investigations of the system dynamics, we obtain that the system presents a chaotic behaviour at weak values of the offset parameters. Routh-Hurwitz criteria are used to study the asymptotic stability of the steady states. An adaptive observer design method is applied to achieve synchronization of two identical MVDPD oscillators with offset. Numerical simulations are given to validate the proposed synchronization approach. Moreover, as an application, the proposed scheme is applied to secure communication. Also, simulation results verify the proposed scheme's success in the communication application

Leader emergence through interpersonal neural synchronization.

Science.gov (United States)

Jiang, Jing; Chen, Chuansheng; Dai, Bohan; Shi, Guang; Ding, Guosheng; Liu, Li; Lu, Chunming

2015-04-07

The neural mechanism of leader emergence is not well understood. This study investigated (i) whether interpersonal neural synchronization (INS) plays an important role in leader emergence, and (ii) whether INS and leader emergence are associated with the frequency or the quality of communications. Eleven three-member groups were asked to perform a leaderless group discussion (LGD) task, and their brain activities were recorded via functional near infrared spectroscopy (fNIRS)-based hyperscanning. Video recordings of the discussions were coded for leadership and communication. Results showed that the INS for the leader-follower (LF) pairs was higher than that for the follower-follower (FF) pairs in the left temporo-parietal junction (TPJ), an area important for social mentalizing. Although communication frequency was higher for the LF pairs than for the FF pairs, the frequency of leader-initiated and follower-initiated communication did not differ significantly. Moreover, INS for the LF pairs was significantly higher during leader-initiated communication than during follower-initiated communications. In addition, INS for the LF pairs during leader-initiated communication was significantly correlated with the leaders' communication skills and competence, but not their communication frequency. Finally, leadership could be successfully predicted based on INS as well as communication frequency early during the LGD (before half a minute into the task). In sum, this study found that leader emergence was characterized by high-level neural synchronization between the leader and followers and that the quality, rather than the frequency, of communications was associated with synchronization. These results suggest that leaders emerge because they are able to say the right things at the right time.

Learning Activities and Discourses in Mathematics Teachers' Synchronous Oral Communication Online

Science.gov (United States)

Erixon, Eva-Lena

2016-01-01

There is increasing interest in the provision of online professional development (OPD) for teachers. This case study contributes to the field of research on professional development in the context of activities and discourses relating to mathematics teachers' synchronous oral communication online. The purpose of this article is to explore the…

Computer Learner Corpora: Analysing Interlanguage Errors in Synchronous and Asynchronous Communication

Science.gov (United States)

MacDonald, Penny; Garcia-Carbonell, Amparo; Carot, Sierra, Jose Miguel

2013-01-01

This study focuses on the computer-aided analysis of interlanguage errors made by the participants in the telematic simulation IDEELS (Intercultural Dynamics in European Education through on-Line Simulation). The synchronous and asynchronous communication analysed was part of the MiLC Corpus, a multilingual learner corpus of texts written by…

Teaching-Learning Process by Synchronic Communication Tools: The Elluminate Live Case

Science.gov (United States)

Santovena-Casal, Sonia Ma

2012-01-01

When integrating a new online tool in university educational system, it is necessary to know its features, applications and functions in depth, advantages and disadvantages, and the results obtained when it has been used by other educational institutions. Synchronous communication tool, "Elluminate Live" can be integrated into a virtual platform…

Performance prediction of a synchronization link for distributed aerospace wireless systems.

Science.gov (United States)

Wang, Wen-Qin; Shao, Huaizong

2013-01-01

For reasons of stealth and other operational advantages, distributed aerospace wireless systems have received much attention in recent years. In a distributed aerospace wireless system, since the transmitter and receiver placed on separated platforms which use independent master oscillators, there is no cancellation of low-frequency phase noise as in the monostatic cases. Thus, high accurate time and frequency synchronization techniques are required for distributed wireless systems. The use of a dedicated synchronization link to quantify and compensate oscillator frequency instability is investigated in this paper. With the mathematical statistical models of phase noise, closed-form analytic expressions for the synchronization link performance are derived. The possible error contributions including oscillator, phase-locked loop, and receiver noise are quantified. The link synchronization performance is predicted by utilizing the knowledge of the statistical models, system error contributions, and sampling considerations. Simulation results show that effective synchronization error compensation can be achieved by using this dedicated synchronization link.

Distributed Synchronization in Communication Networks

Science.gov (United States)

2018-01-24

synchronization. Secondly, it is known that identical oscillators with sin() coupling functions are guaranteed to synchronize in phase on a complete...provide sufficient conditions for phase- locking , i.e., convergence to a stable equilibrium almost surely. We additionally find conditions when the

High-precision shape representation using a neuromorphic vision sensor with synchronous address-event communication interface

Science.gov (United States)

Belbachir, A. N.; Hofstätter, M.; Litzenberger, M.; Schön, P.

2009-10-01

A synchronous communication interface for neuromorphic temporal contrast vision sensors is described and evaluated in this paper. This interface has been designed for ultra high-speed synchronous arbitration of a temporal contrast image sensors pixels' data. Enabling high-precision timestamping, this system demonstrates its uniqueness for handling peak data rates and preserving the main advantage of the neuromorphic electronic systems, that is high and accurate temporal resolution. Based on a synchronous arbitration concept, the timestamping has a resolution of 100 ns. Both synchronous and (state-of-the-art) asynchronous arbiters have been implemented in a neuromorphic dual-line vision sensor chip in a standard 0.35 µm CMOS process. The performance analysis of both arbiters and the advantages of the synchronous arbitration over asynchronous arbitration in capturing high-speed objects are discussed in detail.

High-precision shape representation using a neuromorphic vision sensor with synchronous address-event communication interface

International Nuclear Information System (INIS)

Belbachir, A N; Hofstätter, M; Litzenberger, M; Schön, P

2009-01-01

A synchronous communication interface for neuromorphic temporal contrast vision sensors is described and evaluated in this paper. This interface has been designed for ultra high-speed synchronous arbitration of a temporal contrast image sensors pixels' data. Enabling high-precision timestamping, this system demonstrates its uniqueness for handling peak data rates and preserving the main advantage of the neuromorphic electronic systems, that is high and accurate temporal resolution. Based on a synchronous arbitration concept, the timestamping has a resolution of 100 ns. Both synchronous and (state-of-the-art) asynchronous arbiters have been implemented in a neuromorphic dual-line vision sensor chip in a standard 0.35 µm CMOS process. The performance analysis of both arbiters and the advantages of the synchronous arbitration over asynchronous arbitration in capturing high-speed objects are discussed in detail

A Shared Scratchpad Memory with Synchronization Support

DEFF Research Database (Denmark)

Hansen, Henrik Enggaard; Maroun, Emad Jacob; Kristensen, Andreas Toftegaard

2017-01-01

Multicore processors usually communicate via shared memory, which is backed up by a shared level 2 cache and a cache coherence protocol. However, this solution is not a good fit for real-time systems, where we need to provide tight guarantees on execution and memory access times. In this paper, we...... propose a shared scratchpad memory as a time-predictable communication and synchronization structure, instead of the level 2 cache. The shared on-chip memory is accessed via a time division multiplexing arbiter, isolating the execution time of load and store instructions between processing cores....... Furthermore, the arbiter supports an extended time slot where an atomic load and store instruction can be executed to implement synchronization primitives. In the evaluation we show that a shared scratchpad memory is an efficient communication structure for a small number of processors; in our setup, 9 cores...

FPGA Implementation of a Frame Synchronization Algorithm for Powerline Communications

Directory of Open Access Journals (Sweden)

S. Tsakiris

2009-09-01

Full Text Available This paper presents an FPGA implementation of a pilot–based time synchronization scheme employing orthogonal frequency division multiplexing for powerline communication channels. The functionality of the algorithm is analyzed and tested over a real powerline residential network. For this purpose, an appropriate transmitter circuit, implemented by an FPGA, and suitable coupling circuits are constructed. The system has been developed using VHDL language on Nallatech XtremeDSP development kits. The communication system operates in the baseband up to 30 MHz. Measurements of the algorithm's good performance in terms of the number of detected frames and timing offset error are taken and compared to simulations of existing algorithms.

Design of secure digital communication systems using chaotic modulation, cryptography and chaotic synchronization

International Nuclear Information System (INIS)

Chien, T.-I.; Liao, T.-L.

2005-01-01

This paper presents a secure digital communication system based on chaotic modulation, cryptography, and chaotic synchronization techniques. The proposed system consists of a Chaotic Modulator (CM), a Chaotic Secure Transmitter (CST), a Chaotic Secure Receiver (CSR) and a Chaotic Demodulator (CDM). The CM module incorporates a chaotic system and a novel Chaotic Differential Peaks Keying (CDPK) modulation scheme to generate analog patterns corresponding to the input digital bits. The CST and CSR modules are designed such that a single scalar signal is transmitted in the public channel. Furthermore, by giving certain structural conditions of a particular class of chaotic system, the CST and the nonlinear observer-based CSR with an appropriate observer gain are constructed to synchronize with each other. These two slave systems are driven simultaneously by the transmitted signal and are designed to synchronize and generate appropriate cryptography keys for encryption and decryption purposes. In the CDM module, a nonlinear observer is designed to estimate the chaotic modulating system in the CM. A demodulation mechanism is then applied to decode the transmitted input digital bits. The effectiveness of the proposed scheme is demonstrated through the numerical simulation of an illustrative communication system. Synchronization between the chaotic circuits of the transmitter and receiver modules is guaranteed through the Lyapunov stability theorem. Finally, the security features of the proposed system in the event of attack by an intruder in either the time domain or the frequency domain are discussed

A secure communication system using projective-lag and/or projective-anticipating synchronizations of coupled multidelay feedback systems

International Nuclear Information System (INIS)

Thang Manh Hoang; Nakagawa, Masahiro

2008-01-01

In this paper, a chaotic secure communication system is proposed by using the schemes of projective-lag and/or projective-anticipating synchronizations of coupled multidelay feedback systems and the modulation technique of synchronization-manifold shift keying. Further, the security of the proposed system is enhanced by using non-stationary dynamics in the master and/or non-stationary synchronization manifolds. The specific examples using modified Ikeda systems demonstrate and verify the effectiveness of the proposed system

Effects of Synchronous and Asynchronous Computer-Mediated Communication (CMC) Oral Conversations on English Language Learners' Discourse Functions

Science.gov (United States)

AbuSeileek, Ali Farhan; Qatawneh, Khaleel

2013-01-01

This study aimed to explore the effects of synchronous and asynchronous computer mediated communication (CMC) oral discussions on question types and strategies used by English as a Foreign Language (EFL) learners. The participants were randomly assigned to two treatment conditions/groups; the first group used synchronous CMC, while the second…

Synchronization and secure communication of chaotic systems via robust adaptive high-gain fuzzy observer

International Nuclear Information System (INIS)

Hyun, Chang-Ho; Park, Chang-Woo; Kim, Jae-Hun; Park, Mignon

2009-01-01

This paper proposes an alternative robust adaptive high-gain fuzzy observer design scheme and its application to synchronization and secure communication of chaotic systems. It is assumed that their states are immeasurable and their parameters are unknown. The structure of the proposed observer is represented by Takagi-Sugeno fuzzy model and has the integrator of the estimation error. It improves the performance of high-gain observer and makes the proposed observer robust against noisy measurements, uncertainties and parameter perturbations as well. Using Lyapunov stability theory, an adaptive law is derived to estimate the unknown parameters and the stability of the proposed observer is analyzed. Some simulation result of synchronization and secure communication of chaotic systems is given to present the validity of theoretical derivations and the performance of the proposed observer as an application.

On Synchronization Primitive Systems.

Science.gov (United States)

The report studies the question: what synchronization primitive should be used to handle inter-process communication. A formal model is presented...between these synchronization primitives. Although only four synchronization primitives are compared, the general methods can be used to compare other... synchronization primitives. Moreover, in the definitions of these synchronization primitives, conditional branches are explicitly allowed. In addition

Multiplexing symbolic dynamics-based chaos communications using synchronization

Energy Technology Data Exchange (ETDEWEB)

Blakely, Jonathan N; Corron, Ned J [US Army RDECOM, AMSRD-AMR-WS-ST, Redstone Arsenal, Huntsville, AL 35898 (United States)

2005-01-01

A novel form of multiplexing information-bearing chaotic waveforms is demonstrated experimentally. This scheme dramatically increases the information carrying capacity of a chaotic communication system. In the transmitter, information is encoded in the chaotic waveforms of two electronic circuits using small perturbations to induce the symbolic dynamics to follow a prescribed symbol sequence. Waveforms from each of the drive oscillators are summed to form a single scalar signal that is transmitted to the receiver. Identical oscillators in the receiver synchronize to their counterparts in the drive system, effectively de-multiplexing the transmitted signal. The transmitted information in each channel is extracted from simple return maps of the receiver oscillators.

Multiplexing symbolic dynamics-based chaos communications using synchronization

International Nuclear Information System (INIS)

Blakely, Jonathan N; Corron, Ned J

2005-01-01

A novel form of multiplexing information-bearing chaotic waveforms is demonstrated experimentally. This scheme dramatically increases the information carrying capacity of a chaotic communication system. In the transmitter, information is encoded in the chaotic waveforms of two electronic circuits using small perturbations to induce the symbolic dynamics to follow a prescribed symbol sequence. Waveforms from each of the drive oscillators are summed to form a single scalar signal that is transmitted to the receiver. Identical oscillators in the receiver synchronize to their counterparts in the drive system, effectively de-multiplexing the transmitted signal. The transmitted information in each channel is extracted from simple return maps of the receiver oscillators

A new type of cascading synchronization for halo-chaos and its potential for communication applications

International Nuclear Information System (INIS)

Fang Jinqing; Yu Xinghuo

2004-01-01

Study of beam halo-chaos has become a key issue of concern for many future important applications. Control of halo-chaos has been researched intensively. This is the first time that the synchronization of beam halo-chaos has been realized in this field so far. Two nonlinear feedback control methods are proposed for the cascading synchronizing halo-chaos in coupled lattices of a periodic focusing channel. The simulation results show that the methods are effective. The realization of the synchronization of beam halo-chaos is significant not only for halo-chaos control itself but also for halo-chaos-based secure communication which may become an innovative technique

An Evaluation of optional timing/synchronization features to support selection of an optimum design for the DCS digital communication network

Science.gov (United States)

Bradley, D. B.; Cain, J. B., III; Williard, M. W.

1978-01-01

The task was to evaluate the ability of a set of timing/synchronization subsystem features to provide a set of desirable characteristics for the evolving Defense Communications System digital communications network. The set of features related to the approaches by which timing/synchronization information could be disseminated throughout the network and the manner in which this information could be utilized to provide a synchronized network. These features, which could be utilized in a large number of different combinations, included mutual control, directed control, double ended reference links, independence of clock error measurement and correction, phase reference combining, and self organizing.

Global synchronization of complex dynamical networks through digital communication with limited data rate.

Science.gov (United States)

Wang, Yan-Wu; Bian, Tao; Xiao, Jiang-Wen; Wen, Changyun

2015-10-01

This paper studies the global synchronization of complex dynamical network (CDN) under digital communication with limited bandwidth. To realize the digital communication, the so-called uniform-quantizer-sets are introduced to quantize the states of nodes, which are then encoded and decoded by newly designed encoders and decoders. To meet the requirement of the bandwidth constraint, a scaling function is utilized to guarantee the quantizers having bounded inputs and thus achieving bounded real-time quantization levels. Moreover, a new type of vector norm is introduced to simplify the expression of the bandwidth limit. Through mathematical induction, a sufficient condition is derived to ensure global synchronization of the CDNs. The lower bound on the sum of the real-time quantization levels is analyzed for different cases. Optimization method is employed to relax the requirements on the network topology and to determine the minimum of such lower bound for each case, respectively. Simulation examples are also presented to illustrate the established results.

Design and performance analysis for several new classes of codes for optical synchronous CDMA and for arbitrary-medium time-hopping synchronous CDMA communication systems

Science.gov (United States)

Kostic, Zoran; Titlebaum, Edward L.

1994-08-01

New families of spread-spectrum codes are constructed, that are applicable to optical synchronous code-division multiple-access (CDMA) communications as well as to arbitrary-medium time-hopping synchronous CDMA communications. Proposed constructions are based on the mappings from integer sequences into binary sequences. We use the concept of number theoretic quadratic congruences and a subset of Reed-Solomon codes similar to the one utilized in the Welch-Costas frequency-hop (FH) patterns. The properties of the codes are as good as or better than the properties of existing codes for synchronous CDMA communications: Both the number of code-sequences within a single code family and the number of code families with good properties are significantly increased when compared to the known code designs. Possible applications are presented. To evaluate the performance of the proposed codes, a new class of hit arrays called cyclical hit arrays is recalled, which give insight into the previously unknown properties of the few classes of number theoretic FH patterns. Cyclical hit arrays and the proposed mappings are used to determine the exact probability distribution functions of random variables that represent interference between users of a time-hopping or optical CDMA system. Expressions for the bit error probability in multi-user CDMA systems are derived as a function of the number of simultaneous CDMA system users, the length of signature sequences and the threshold of a matched filter detector. The performance results are compared with the results for some previously known codes.

Listener-Performer Synchronicity in Recorded Performances of Chopin’s Mazurkas

Directory of Open Access Journals (Sweden)

Mitchell Ohriner

2015-01-01

Full Text Available Studies of duration in music performance since the 1980s have focused on the role of duration in the communication of musical structure, in particular grouping and metric structure. This article posits a broader view of duration in performance; that performers choose durations to facilitate or inhibit listener-performer synchronicity. Listeners who maintain synchronicity are continually rewarded for making accurate predictions of when events will happen, and thus the loss of synchronicity might hazard feelings of frustration or isolation. Performers, by choosing durations that are difficult to predict, can therefore enlist these feelings in dynamic narratives of synchronicity that augment trajectories in the score. The article explores two such narratives, found in two idiosyncratic renditions of passages of Chopin’s mazurkas and echoed by seventeen participants’ attempts to synchronize with them. By ascribing significance not only to the choices of performers and composers but also to how individual listeners attend to those choices, the article aims to widen the circle of agencies ascribed with the ability to affect the meaning of musical works.

Can Synchronous Computer-Mediated Communication (CMC) Help Beginning-Level Foreign Language Learners Speak?

Science.gov (United States)

Ko, Chao-Jung

2012-01-01

This study investigated the possibility that initial-level learners may acquire oral skills through synchronous computer-mediated communication (SCMC). Twelve Taiwanese French as a foreign language (FFL) students, divided into three groups, were required to conduct a variety of tasks in one of the three learning environments (video/audio, audio,…

A novel sort of adaptive complex synchronizations of two indistinguishable chaotic complex nonlinear models with uncertain parameters and its applications in secure communications

Science.gov (United States)

Mahmoud, Emad E.; Abood, Fatimah S.

In this paper, we will demonstrate the adaptive complex anti-lag synchronization (CALS) of two indistinguishable complex chaotic nonlinear systems with the parameters which are uncertain. The significance of CALS is not advised well in the literature yet. The CALS contains or consolidate two sorts of synchronizations (anti-lag synchronization ALS and lag synchronization LS). The state variable of the master system synchronizes with an alternate state variable of the slave system. Depending on the function of Lyapunov, a plan is orchestrated to achieve CALS of chaotic attractors of complex systems with unverifiable parameters. CALS of two indistinguishable complexes of Lü systems is viewed as, for example, an occasion for affirming the likelihood of the plan exhibited. In physics, we can see complex chaotic systems in numerous different applications, for example, applied sciences or engineering. With a specific end goal to affirm the proposed synchronization plan viability and demonstrate the hypothetical outcomes, we can compute the numerical simulation. The above outcomes will give the hypothetical establishment to the secure communication applications. CALS of complex chaotic systems in which a state variable of the master system synchronizes with an alternate state variable of the slave system is an encouraging sort of synchronization as it contributes excellent security in secure communication. Amid this secure communication, the synchronization between transmitter and collector is shut and message signals are recouped. The encryption and restoration of the signals are simulated numerically.

Learners' Use of Communication Strategies in Text-Based and Video-Based Synchronous Computer-Mediated Communication Environments: Opportunities for Language Learning

Science.gov (United States)

Hung, Yu-Wan; Higgins, Steve

2016-01-01

This study investigates the different learning opportunities enabled by text-based and video-based synchronous computer-mediated communication (SCMC) from an interactionist perspective. Six Chinese-speaking learners of English and six English-speaking learners of Chinese were paired up as tandem (reciprocal) learning dyads. Each dyad participated…

Forced synchronization of large-scale circulation to increase predictability of surface states

Science.gov (United States)

Shen, Mao-Lin; Keenlyside, Noel; Selten, Frank; Wiegerinck, Wim; Duane, Gregory

2016-04-01

Numerical models are key tools in the projection of the future climate change. The lack of perfect initial condition and perfect knowledge of the laws of physics, as well as inherent chaotic behavior limit predictions. Conceptually, the atmospheric variables can be decomposed into a predictable component (signal) and an unpredictable component (noise). In ensemble prediction the anomaly of ensemble mean is regarded as the signal and the ensemble spread the noise. Naturally the prediction skill will be higher if the signal-to-noise ratio (SNR) is larger in the initial conditions. We run two ensemble experiments in order to explore a way to reduce the SNR of surface winds and temperature. One ensemble experiment is AGCM with prescribing sea surface temperature (SST); the other is AGCM with both prescribing SST and nudging the high-level temperature and winds to ERA-Interim. Each ensemble has 30 members. Larger SNR is expected and found over the tropical ocean in the first experiment because the tropical circulation is associated with the convection and the associated surface wind convergence as these are to a large extent driven by the SST. However, small SNR is found over high latitude ocean and land surface due to the chaotic and non-synchronized atmosphere states. In the second experiment the higher level temperature and winds are forced to be synchronized (nudged to reanalysis) and hence a larger SNR of surface winds and temperature is expected. Furthermore, different nudging coefficients are also tested in order to understand the limitation of both synchronization of large-scale circulation and the surface states. These experiments will be useful for the developing strategies to synchronize the 3-D states of atmospheric models that can be later used to build a super model.

Mutually Beneficial Foreign Language Learning: Creating Meaningful Interactions through Video-Synchronous Computer-Mediated Communication

Science.gov (United States)

Kato, Fumie; Spring, Ryan; Mori, Chikako

2016-01-01

Providing learners of a foreign language with meaningful opportunities for interactions, specifically with native speakers, is especially challenging for instructors. One way to overcome this obstacle is through video-synchronous computer-mediated communication tools such as Skype software. This study reports quantitative and qualitative data from…

High Precision Clock Bias Prediction Model in Clock Synchronization System

Directory of Open Access Journals (Sweden)

Zan Liu

2016-01-01

Full Text Available Time synchronization is a fundamental requirement for many services provided by a distributed system. Clock calibration through the time signal is the usual way to realize the synchronization among the clocks used in the distributed system. The interference to time signal transmission or equipment failures may bring about failure to synchronize the time. To solve this problem, a clock bias prediction module is paralleled in the clock calibration system. And for improving the precision of clock bias prediction, the first-order grey model with one variable (GM(1,1 model is proposed. In the traditional GM(1,1 model, the combination of parameters determined by least squares criterion is not optimal; therefore, the particle swarm optimization (PSO is used to optimize GM(1,1 model. At the same time, in order to avoid PSO getting stuck at local optimization and improve its efficiency, the mechanisms that double subgroups and nonlinear decreasing inertia weight are proposed. In order to test the precision of the improved model, we design clock calibration experiments, where time signal is transferred via radio and wired channel, respectively. The improved model is built on the basis of clock bias acquired in the experiments. The results show that the improved model is superior to other models both in precision and in stability. The precision of improved model increased by 66.4%~76.7%.

Carrier and symbol synchronization system performance study

Science.gov (United States)

Lindsey, W. C.

1976-01-01

Results pertinent to predicting the performance of convolutionally encoded binary phase-shift keyed communication links were presented. The details of the development are provided in four sections. These sections are concerned with developing the bit error probability performance degradations due to PN despreading by a time-shared delay locked loop, the Costas demodulation process, symbol synchronization effects and cycle slipping phenomena in the Costas loop. In addition, Costas cycle slipping probabilities are studied as functions of Doppler count time and signal-to-noise conditions. The effect of cycle slipping in the symbol synchronizer is also studied as a function of channel Doppler and other frequency uncertainties.

The Use of Skype as a Synchronous Communication Tool between Foreign Language College Students and Native Speakers

Science.gov (United States)

Guerrero, Mario

2012-01-01

The rapid growth and interest of college students in Computer Mediated Communication and social media have impacted the second language learning and teaching process. This article reports on a pilot project that attempts to analyze the use of Skype as a synchronous communication tool in regard to the attitudes of students in learning a foreign…

Numerical Simulation Bidirectional Chaotic Synchronization of Spiegel-Moore Circuit and Its Application for Secure Communication

Science.gov (United States)

Sanjaya, W. S. M.; Anggraeni, D.; Denya, R.; Ismail, N.

2017-03-01

Spiegel-Moore is a dynamical chaotic system which shows irregular variability in the luminosity of stars. In this paper present the performed the design and numerical simulation of the synchronization Spiegel-Moore circuit and applied to security system for communication. The initial study in this paper is to analyze the eigenvalue structures, various attractors, Bifurcation diagram, and Lyapunov exponent analysis. We have studied the dynamic behavior of the system in the case of the bidirectional coupling via a linear resistor. Both experimental and simulation results have shown that chaotic synchronization is possible. Finally, the effectiveness of the bidirectional coupling scheme between two identical Spiegel-Moore circuits in a secure communication system is presented in details. Integration of theoretical electronic circuit, the numerical simulation by using MATLAB®, as well as the implementation of circuit simulations by using Multisim® has been performed in this study.

Novel Blind Recognition Algorithm of Frame Synchronization Words Based on Soft-Decision in Digital Communication Systems.

Science.gov (United States)

Qin, Jiangyi; Huang, Zhiping; Liu, Chunwu; Su, Shaojing; Zhou, Jing

2015-01-01

A novel blind recognition algorithm of frame synchronization words is proposed to recognize the frame synchronization words parameters in digital communication systems. In this paper, a blind recognition method of frame synchronization words based on the hard-decision is deduced in detail. And the standards of parameter recognition are given. Comparing with the blind recognition based on the hard-decision, utilizing the soft-decision can improve the accuracy of blind recognition. Therefore, combining with the characteristics of Quadrature Phase Shift Keying (QPSK) signal, an improved blind recognition algorithm based on the soft-decision is proposed. Meanwhile, the improved algorithm can be extended to other signal modulation forms. Then, the complete blind recognition steps of the hard-decision algorithm and the soft-decision algorithm are given in detail. Finally, the simulation results show that both the hard-decision algorithm and the soft-decision algorithm can recognize the parameters of frame synchronization words blindly. What's more, the improved algorithm can enhance the accuracy of blind recognition obviously.

Synchronizing Strategies under Partial Observability

DEFF Research Database (Denmark)

Larsen, Kim Guldstrand; Laursen, Simon; Srba, Jiri

2014-01-01

Embedded devices usually share only partial information about their current configurations as the communication bandwidth can be restricted. Despite this, we may wish to bring a failed device into a given predetermined configuration. This problem, also known as resetting or synchronizing words, has...... been intensively studied for systems that do not provide any information about their configurations. In order to capture more general scenarios, we extend the existing theory of synchronizing words to synchronizing strategies, and study the synchronization, short-synchronization and subset...

Mechanism for Promoting Motivation, Confidence, and Autonomy through Synchronic Communication Sessions in Virtual Learning Environments

Science.gov (United States)

Valencia, Jorge Andrick Parra; Dallos, Adriana Rocío Lizcano; Ballesteros, Eliécer Pineda

2017-01-01

This study presents a mechanism which explains the effect of synchronous communication on students' perception of the training process in virtual learning methodology used in a postgraduate programme at the University of Santander. We use System Dynamics to design a mechanism that integrates motivation, confidence, trust, and autonomy in students.…

In-Home Synchronous Telespeech Therapy to Improve Functional Communication in Chronic Poststroke Aphasia: Results from a Quasi-Experimental Study.

Science.gov (United States)

Macoir, Joël; Sauvageau, Vincent Martel; Boissy, Patrick; Tousignant, Marilyn; Tousignant, Michel

2017-08-01

Although the use of telepractice in speech-language therapy for assessment purposes is well documented, its effectiveness and potential for rehabilitation in poststroke aphasia remain largely unknown. The purpose of this study was to investigate the effectiveness of a remotely delivered synchronous pragmatic telespeech language therapy for improving functional communication in aphasia. A pre-/post-test design was chosen in which each participant was his or her own control. Using a telerehabilitation platform and software (Oralys TeleTherapy) based on the Promoting Aphasics' Communicative Effectiveness (PACE) approach, 20 participants with chronic poststroke aphasia received 9 speech therapy sessions over a 3-week period. Teletreatment with the PACE pragmatic rehabilitation approach led to improvements in functional communication, marked by (a) an increase in communication effectiveness, reflecting significantly improved autonomy in functional communication; (b) a decrease in communication exchange duration, meaning that the treatment made communication faster and more efficient; (c) a decrease in the number of communication acts, meaning that, after treatment, less information was needed to be efficiently understood by the communication partner; and (d) an increase in the number of different communication strategies used, meaning that the treatment fostered the use of a variety of alternative communication modes. This study provides additional arguments about the benefits of telerehabilitation for poststroke patients with aphasia. It showed that multimodal language therapy delivered through synchronous telerehabilitation had positive effects on functional communication in chronic aphasia.

Reviving a Digital Dinosaur: Text-Only Synchronous Online Chats and Peer Tutoring in Communication Centers

Science.gov (United States)

Schwartzman, Roy

2013-01-01

A qualitative and quantitative content analysis was conducted of all text-based synchronous online chats at an oral communication peer tutoring center throughout a semester. As a comparative benchmark, chats at the same university's main library were analyzed over the same time period. The library's chats were much more heavily weighted toward…

Novel Blind Recognition Algorithm of Frame Synchronization Words Based on Soft-Decision in Digital Communication Systems.

Directory of Open Access Journals (Sweden)

Jiangyi Qin

Full Text Available A novel blind recognition algorithm of frame synchronization words is proposed to recognize the frame synchronization words parameters in digital communication systems. In this paper, a blind recognition method of frame synchronization words based on the hard-decision is deduced in detail. And the standards of parameter recognition are given. Comparing with the blind recognition based on the hard-decision, utilizing the soft-decision can improve the accuracy of blind recognition. Therefore, combining with the characteristics of Quadrature Phase Shift Keying (QPSK signal, an improved blind recognition algorithm based on the soft-decision is proposed. Meanwhile, the improved algorithm can be extended to other signal modulation forms. Then, the complete blind recognition steps of the hard-decision algorithm and the soft-decision algorithm are given in detail. Finally, the simulation results show that both the hard-decision algorithm and the soft-decision algorithm can recognize the parameters of frame synchronization words blindly. What's more, the improved algorithm can enhance the accuracy of blind recognition obviously.

Dead Zone Oscillator Control for Communication-Free Synchronization of Paralleled, Three-Phase, Current-Controlled Inverters

Science.gov (United States)

2016-05-11

Current-Controlled Inverters by Midshipman 1/C Spencer C. Shabshab, USN UNITED STATES NAVAL ACADEMY...Three-Phase, Current-Controlled Inverters by Midshipman 1/C Spencer C. Shabshab United States Naval Academy Annapolis, Maryland...for Communication-Free Synchronization of Paralleled, 5a. CONTRACT NUMBER Three-Phase, Current-Controlled Inverters 5b. GRANT NUMBER 5c

Prediction of chaos in non-salient permanent-magnet synchronous machines

Energy Technology Data Exchange (ETDEWEB)

Rasoolzadeh, Arsalan [Department of Electrical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of); Tavazoei, Mohammad Saleh, E-mail: tavazoei@sharif.edu [Department of Electrical Engineering, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

2012-12-03

This Letter tries to find the area in parameter space of a non-salient Permanent-Magnet Synchronous Machine (PMSM) in which chaos can occur. This area is briefly named as chaotic area. The predicted chaotic area is obtained by checking some conditions which are necessary for existence of chaos in a dynamical system. In this Letter, it is assumed that this machine is in the generator mode, and its model is based on direct and quadrature axis of stator voltages and currents. The information of the predicted area is used in non-chaotic maximum power control of torque in the machine.

RUN LENGTH SYNCHRONIZATION TECHNIQUES

Science.gov (United States)

An important aspect of digital communications is the problem of determining efficient methods for acquiring block synchronization . In this paper we...utilizes an N-digit sync sequence as prefix to the data blocks. The results of this study show that this technique is a practical method for acquiring block synchronization .

Lag synchronization of hyperchaos with application to secure communications

International Nuclear Information System (INIS)

Li Chuandong; Liao Xiaofeng; Wong Kwokwo

2005-01-01

In this paper, hyperchaotic lag synchronization is restated as a nonlinear and lag-in-time observer design issue. This approach leads to a systematic tool, which guarantees the lag synchronization of a wide class of chaotic or hyperchaotic systems via a scalar signal. By exploiting this result, we propose a hyperchaos-based cryptosystem scheme that combines the conventional cryptographic methods and the lag synchronization of chaotic circuits. The computer simulation results show that the lag synchronization scheme and the cryptosystem proposed in this paper are both feasible

Synchronization of hyperchaotic oscillators

DEFF Research Database (Denmark)

Tamasevicius, A.; Cenys, A.; Mykolaitis, G.

1997-01-01

Synchronization of chaotic oscillators is believed to have promising applications in secure communications. Hyperchaotic systems with multiple positive Lyapunov exponents (LEs) have an advantage over common chaotic systems with only one positive LE. Three different types of hyperchaotic electronic...... oscillators are investigated demonstrating synchronization by means of only one properly selected variable....

Two novel synchronization criterions for a unified chaotic system

International Nuclear Information System (INIS)

Tao Chaohai; Xiong Hongxia; Hu Feng

2006-01-01

Two novel synchronization criterions are proposed in this paper. It includes drive-response synchronization and adaptive synchronization schemes. Moreover, these synchronization criterions can be applied to a large class of chaotic systems and are very useful for secure communication

Mathematical Modelling and Predictive Control of Permanent Magnet Synchronous Motor Drives

Czech Academy of Sciences Publication Activity Database

Belda, Květoslav

2013-01-01

Roč. 2, č. 4 (2013), s. 114-120 ISSN 1805-3386 R&D Projects: GA ČR(CZ) GAP102/11/0437 Institutional support: RVO:67985556 Keywords : Permanent magnet synchronous motor * mathematical modelling * discrete predictive control * multistep explicit control law * square-root optimization Subject RIV: BC - Control Systems Theory http://library.utia.cas.cz/separaty/2014/AS/belda-0422285.pdf

Transmission delays in hardware clock synchronization

Science.gov (United States)

Shin, Kang G.; Ramanathan, P.

1988-01-01

Various methods, both with software and hardware, have been proposed to synchronize a set of physical clocks in a system. Software methods are very flexible and economical but suffer an excessive time overhead, whereas hardware methods require no time overhead but are unable to handle transmission delays in clock signals. The effects of nonzero transmission delays in synchronization have been studied extensively in the communication area in the absence of malicious or Byzantine faults. The authors show that it is easy to incorporate the ideas from the communication area into the existing hardware clock synchronization algorithms to take into account the presence of both malicious faults and nonzero transmission delays.

Synchronization of an Inertial Neural Network With Time-Varying Delays and Its Application to Secure Communication.

Science.gov (United States)

Lakshmanan, Shanmugam; Prakash, Mani; Lim, Chee Peng; Rakkiyappan, Rajan; Balasubramaniam, Pagavathigounder; Nahavandi, Saeid

2018-01-01

In this paper, synchronization of an inertial neural network with time-varying delays is investigated. Based on the variable transformation method, we transform the second-order differential equations into the first-order differential equations. Then, using suitable Lyapunov-Krasovskii functionals and Jensen's inequality, the synchronization criteria are established in terms of linear matrix inequalities. Moreover, a feedback controller is designed to attain synchronization between the master and slave models, and to ensure that the error model is globally asymptotically stable. Numerical examples and simulations are presented to indicate the effectiveness of the proposed method. Besides that, an image encryption algorithm is proposed based on the piecewise linear chaotic map and the chaotic inertial neural network. The chaotic signals obtained from the inertial neural network are utilized for the encryption process. Statistical analyses are provided to evaluate the effectiveness of the proposed encryption algorithm. The results ascertain that the proposed encryption algorithm is efficient and reliable for secure communication applications.

Perceived Benefits and Drawbacks of Synchronous Voice-Based Computer-Mediated Communication in the Foreign Language Classroom

Science.gov (United States)

Bueno Alastuey, M. C.

2011-01-01

This study explored the benefits and drawbacks of synchronous voice-based computer-mediated communication (CMC) in a blended course of English for specific purposes. Quantitative and qualitative data from two groups following the same syllabus, except for the oral component, were compared. Oral tasks were carried out face-to-face with same L1…

A synchronous communication experiment within an online distance learning program: a case study.

Science.gov (United States)

Boulos, Maged N Kamel; Taylor, Andrea D; Breton, Alice

2005-10-01

Student-teacher and student-student interactions in purely asynchronous distance learning courses are much lacking compared to similar interactions found in face-to-face teaching, causing learners to experience feelings of isolation, thus reducing motivation and increasing dropout rates. We used PalTalk, an Internet text and audio chat client from AVM Software, Inc. (New York, NY), to offer our students live virtual classroom sessions within a unit of our online distance learning M.Sc. program in Healthcare Informatics. On-demand replays of audio excerpts from the sessions were also provided to accommodate absenteeism and for student review. Five students completed an evaluation questionnaire. Our results highlighted the potential merits of using synchronous conferencing to assist in fostering a sense of belonging to one supportive learning community among distance learners and improve educational outcomes. Students were very positive toward the real-time human interaction and voted for a 95/5 (asynchronous/synchronous percentages) blended delivery approach for a typical unit in our program. They also praised PalTalk's voice quality and ease of use. This paper presents educational and technological perspectives about this experiment in the form of a state-of the- art review, without intending to be statistically rigorous. However, robust research evidence is still required to convince educators fully about the benefits of synchronous communication tools and help them decide on the most suitable solutions for their particular circumstances.

Prediction of partial synchronization in delay-coupled nonlinear oscillators, with application to Hindmarsh–Rose neurons

International Nuclear Information System (INIS)

Ünal, Hakkı Ulaş; Michiels, Wim

2013-01-01

The full synchronization of coupled nonlinear oscillators has been widely studied. In this paper we investigate conditions for which partial synchronization of time-delayed diffusively coupled systems arises. The coupling configuration of the systems is described by a directed graph. As a novel quantitative result we first give necessary and sufficient conditions for the presence of forward invariant sets characterized by partially synchronous motion. These conditions can easily be checked from the eigenvalues and eigenvectors of the graph Laplacian. Second, we perform stability analysis of the synchronized equilibria in a (gain,delay) parameter space. For this analysis the coupled nonlinear systems are linearized around the synchronized equilibria and then the resulting characteristic function is factorized. By such a factorization, it is shown that the relation between the behaviour of different agents at the zero of the characteristic function depends on the structure of the eigenvectors of the weighted Laplacian matrix. By determining the structure of the solutions in the unstable manifold, combined with the characterization of invariant sets, we predict which partially synchronous regimes occur and estimate the corresponding coupling gain and delay values. We apply the obtained results to networks of coupled Hindmarsh–Rose neurons and verify the occurrence of the expected partially synchronous regimes by using a numerical simulation. We also make a comparison with an existing approach based on Lyapunov functionals. (paper)

Distance learning through synchronous interactive television.

Science.gov (United States)

Hall, Janis L

2007-01-01

The advent and popularity of asynchronous online learning has somewhat obscured a standby technology developed over the last two decades. Interactive videoconferencing, sometimes called "interactive television," though not as glamorous and popular a topic at distance-learning conferences, is still alive and well at many institutions. Three or four years ago, many of us were led to believe that interactive television would go the way of the dinosaurs-everything would soon be in an asynchronous format or on individual desktops. There would no longer be any need for elaborately designed classrooms, networks, and operations staff. To date, this prediction has not come true. In fact, synchronous interactive television has experienced significant growth as newer, easier, and cheaper technologies allow institutions to reach more students with less resource investment. Faculty and students, while appreciating the convenience of asynchronous delivery, still express a need for synchronous communication. This article explores the issues involved in synchronous distance education, the current technologies and proposed future developments, and best practices in terms of classroom design, faculty use, and operational issues. It is not a research article but an anecdotal case study based on Washington State University's experiences over the last 20 years in developing and adapting to new synchronous technologies and creating the support and technical infrastructure to best deliver academic courses through this medium.

Effects of Synchronous Computer-Mediated Communication and Face-to-Face Interaction on Speaking Skill Development of Iranian EFL Learners

OpenAIRE

Hakimeh Shahrokhi Mehr; Masoud Zoghi; Nader Assadi

2013-01-01

The traditional form of teaching speaking skill has been via face-to-face (FTF) interaction in the classroom setting. Today in the computer age, the on-line forum can provide a virtual environment for differential communication. The pedagogical system benefits from such technology improvement for teaching foreign languages. This quasi-experimental research aimed at comparing the effects of two instructional strategies: synchronous computer-mediated communication (SCMC) and FTF interaction. Fo...

Online Teaching and Learning at the Graduate School Level: Student Perceptions on Discussion Boards v. Synchronous Communication

Directory of Open Access Journals (Sweden)

Christopher N. Amos Sr.

2014-06-01

Full Text Available This paper examines a group of graduate students and their previous experiences with online education, various teaching and learning online tools, and their perceptions on the effectiveness of these tools as it relates to their learning, interpersonal skills and communication. This paper presents the graduate student's self-reported educational experience at a regional state university in the southeast United States in a 100% online Master's Degree program. The data was collected through the use of a 28 open-ended question survey, which was completed by a group of 127 graduate students and the findings produced six main findings, which were: 1 The respondents indicated at a high percentage (85% a high level (level 4, 5 and 6 of technology use and understanding. 2 The majority of the respondents (97% indicated they preferred live synchronous sessions rather than discussion boards for learning content and communication. 3 The majority of the respondents (72% indicated that when choosing future courses, the inclusion of discussion boards in a course was not important (34% or somewhat unimportant (38%. 4 100% of the respondents indicated that Live Elluminate Sessions were Highly Effective (65% or Somewhat Effective (35%, as it pertained to understanding the content. 5 Respondents indicated that 59% (12% Highly Effective, 47% Somewhat Effective of the respondents indicated discussion boards as an impactful way of learning content at the graduate level. It also shows that 41% (22% Somewhat Ineffective, 19% Not Effective. This study helps universities identify the importance of synchronous learning in a digital format when delivering online teaching and learning. There is a clear change in the needs of students enrolled in 100% online courses, which will force university faculty to increase the synchronous interaction between them and their students and between the students and their peers. Keywords: Synchronous learning, discussion boards, Blackboard

The Importance of Synchronous Interaction for Student Satisfaction with Course Web Sites

Science.gov (United States)

Cao, Qidong; Griffin, Thomas E.; Bai, Xue

2009-01-01

As more affordable synchronous communications are becoming available, the use of synchronous interactions has not been noted in course Web sites as often as asynchronous communications. Previous research indicated that the integration of synchronous tools into course Web sites has made a positive impact on students. While most of the previous…

Dynamical Analysis, Synchronization, Circuit Design, and Secure Communication of a Novel Hyperchaotic System

Directory of Open Access Journals (Sweden)

Li Xiong

2017-01-01

Full Text Available This paper is devoted to introduce a novel fourth-order hyperchaotic system. The hyperchaotic system is constructed by adding a linear feedback control level based on a modified Lorenz-like chaotic circuit with reduced number of amplifiers. The local dynamical entities, such as the basic dynamical behavior, the divergence, the eigenvalue, and the Lyapunov exponents of the new hyperchaotic system, are all investigated analytically and numerically. Then, an active control method is derived to achieve global chaotic synchronization of the novel hyperchaotic system through making the synchronization error system asymptotically stable at the origin based on Lyapunov stability theory. Next, the proposed novel hyperchaotic system is applied to construct another new hyperchaotic system with circuit deformation and design a new hyperchaotic secure communication circuit. Furthermore, the implementation of two novel electronic circuits of the proposed hyperchaotic systems is presented, examined, and realized using physical components. A good qualitative agreement is shown between the simulations and the experimental results around 500 kHz and below 1 MHz.

Is synchronous computermediated communication a viable ...

African Journals Online (AJOL)

Employing a conversationanalytic perspective, the logs were analysed to determine whether the interaction reflected in them replicated that characteristic of face-to-face classroom interaction. Once the discourse study had been completed, the logs were used to determine learners' perceptions of synchronous learning.

Biologically Inspired Intercellular Slot Synchronization

Directory of Open Access Journals (Sweden)

Alexander Tyrrell

2009-01-01

Full Text Available The present article develops a decentralized interbase station slot synchronization algorithm suitable for cellular mobile communication systems. The proposed cellular firefly synchronization (CelFSync algorithm is derived from the theory of pulse-coupled oscillators, common to describe synchronization phenomena in biological systems, such as the spontaneous synchronization of fireflies. In order to maintain synchronization among base stations (BSs, even when there is no direct link between adjacent BSs, some selected user terminals (UTs participate in the network synchronization process. Synchronization emerges by exchanging two distinct synchronization words, one transmitted by BSs and the other by active UTs, without any a priori assumption on the initial timing misalignments of BSs and UTs. In large-scale networks with inter-BS site distances up to a few kilometers, propagation delays severely affect the attainable timing accuracy of CelFSync. We show that by an appropriate combination of CelFSync with the timing advance procedure, which aligns uplink transmission of UTs to arrive simultaneously at the BS, a timing accuracy within a fraction of the inter-BS propagation delay is retained.

A Non-symmetric Digital Image Secure Communication Scheme Based on Generalized Chaos Synchronization System

International Nuclear Information System (INIS)

Zhang Xiaohong; Min Lequan

2005-01-01

Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color (RGB) digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decrypt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.

Variable selection based on clustering analysis for improvement of polyphenols prediction in green tea using synchronous fluorescence spectra

Science.gov (United States)

Shan, Jiajia; Wang, Xue; Zhou, Hao; Han, Shuqing; Riza, Dimas Firmanda Al; Kondo, Naoshi

2018-04-01

Synchronous fluorescence spectra, combined with multivariate analysis were used to predict flavonoids content in green tea rapidly and nondestructively. This paper presented a new and efficient spectral intervals selection method called clustering based partial least square (CL-PLS), which selected informative wavelengths by combining clustering concept and partial least square (PLS) methods to improve models’ performance by synchronous fluorescence spectra. The fluorescence spectra of tea samples were obtained and k-means and kohonen-self organizing map clustering algorithms were carried out to cluster full spectra into several clusters, and sub-PLS regression model was developed on each cluster. Finally, CL-PLS models consisting of gradually selected clusters were built. Correlation coefficient (R) was used to evaluate the effect on prediction performance of PLS models. In addition, variable influence on projection partial least square (VIP-PLS), selectivity ratio partial least square (SR-PLS), interval partial least square (iPLS) models and full spectra PLS model were investigated and the results were compared. The results showed that CL-PLS presented the best result for flavonoids prediction using synchronous fluorescence spectra.

Method of synchronizing independent functional unit

Science.gov (United States)

Kim, Changhoan

2018-03-13

A system for synchronizing parallel processing of a plurality of functional processing units (FPU), a first FPU and a first program counter to control timing of a first stream of program instructions issued to the first FPU by advancement of the first program counter; a second FPU and a second program counter to control timing of a second stream of program instructions issued to the second FPU by advancement of the second program counter, the first FPU is in communication with a second FPU to synchronize the issuance of a first stream of program instructions to the second stream of program instructions and the second FPU is in communication with the first FPU to synchronize the issuance of the second stream program instructions to the first stream of program instructions.

Synchronous Communication in a Web-Based Senior High School Course: Maximizing Affordances and Minimizing Constraints of the Tool

Science.gov (United States)

Murphy, Elizabeth; Coffin, George

2003-01-01

Researchers studied the use of a suite of synchronous communication tools in support of a Web-based, senior high school French course whose students were dispersed over the vast, sparsely populated province of Newfoundland and Labrador, Canada. The objective was to describe interaction according to four types: student-teacher, student-student,…

Distributed cooperative synchronization strategy for multi-bus microgrids

DEFF Research Database (Denmark)

Sun, Yao; Zhong, Chaolu; Hou, Xiaochao

2017-01-01

Microgrids can operate in both grid-connected mode and islanded mode. In order to smooth transfer from islanded mode to grid-connected mode, it is necessary to synchronize the point of common coupling (PCC) with main utility grid (UG) in voltage frequency, phase and amplitude. Conventional...... synchronization methods based on centralized communication are very costly and not suitable for multi-bus microgrids that have a large number of distributed generators (DGs). To address this concern, this study presents an active synchronization control strategy based on distributed cooperation technology...... for multi-bus microgrids. The proposed method can reconnect the microgrid in island to UG seamlessly with sparse communication channels. Synchronization correction signals are generated by a voltage controller, which are only transmitted to the leader DGs. Meanwhile, each DG exchanges information with its...

Sliding mode control for synchronization of Roessler systems with time delays and its application to secure communication

International Nuclear Information System (INIS)

Chen, C-K; Yan, J-J; Liao, T-L

2007-01-01

This study is concerned with the chaos synchronization problem of Roessler systems subjected to multiple time delays. Based on the sliding mode control (SMC) technique, we first propose an adaptive switching surface which does not allow for a reduction of system order, as is the case in most SMC schemes. Then both a sliding mode controller and a new sufficient condition are derived to guarantee, respectively, the global hitting of the sliding mode and stability of the equivalent error dynamics in the sliding mode. Thus, the chaos synchronization for Roessler systems with multiple time delays can surely be achieved. Moreover, the proposed scheme is then applied to the secure communication system. Numerical simulations are included to demonstrate the feasibility of the proposed scheme

Farm batch system and Fermi inter-process communication and synchronization toolkit

International Nuclear Information System (INIS)

Mandrichenko, I.V.

2001-01-01

Farms Batch System (FBS) was developed as a batch process management system for off-line Run II data processing at Fermilab. FBS will manage PC farms composed of up to 250 nodes and scalable to 1000 nodes with disk capacity of up to several TB. FBS allows users to start arrays of parallel processes on multiple computers. It uses a simplified resource counting method load balancing. FBS has been successfully used for more than a year at Fermilab by fixed target experiments and will be used for collider experiment off-line data processing. Fermi Inter-Process Communication toolkit (FIPC) was designed as a supplement product for FBS that helps establish synchronization and communication between processes running in a distributed batch environment. However, FIPC is an independent package, and can be used with other batch systems, as well as in a non-batch environment. FIPC provides users with a variety of global distributed objects such as semaphores, queues and string variables. Other types of objects can be easily added to FIPC. FIPC has been running on several PC farms at Fermilab for half a year and is going to be used by CDF for off-line data processing

A non-correlator-based digital communication system using interleaved chaotic differential peaks keying (I-CDPK) modulation and chaotic synchronization

International Nuclear Information System (INIS)

Chien, T.-I; Hung, Y.-C.; Liao, T.-L.

2006-01-01

This paper presents a novel non-correlator-based digital communication system with the application of interleaved chaotic differential peaks keying (I-CDPK) modulation technique. The proposed communication system consists of four major modules: I-CDPK modulator (ICM), frequency modulation (FM) transmitter, FM receiver and I-CDPK demodulator (ICDM). In the ICM module, there are four components: a chaotic circuit to generate the chaotic signals, A/D converter, D/A converter and a digital processing mechanism to control all signal flows and performs I-CDPK modulation corresponding to the input digital bits. For interleaving every input digital bit set, every state of the chaotic system is used to represent one portion of it, but only a scalar state variable (i.e. the system output) is sent to the ICDM's chaotic circuit through both FM transmitter and FM receiver. An observer-based chaotic synchronization scheme is designed to synchronize the chaotic circuits of the ICM and ICDM. Meanwhile, the bit detector in ICDM is devoted to recover the transmitted input digital bits. Some numerical simulations of an illustrative communication system are given to demonstrate its theoretical effectiveness. Furthermore, the performance of bit error rate of the proposed system is analyzed and compared with those of the correlator-based communication systems adopting coherent binary phase shift keying (BPSK) and coherent differential chaotic shift keying (DCSK) schemes

Data-derived symbol synchronization of MASK and QASK signals. [for multilevel digital communication systems

Science.gov (United States)

Simon, M. K.

1974-01-01

Multilevel amplitude-shift-keying (MASK) and quadrature amplitude-shift-keying (QASK) as signaling techniques for multilevel digital communications systems, and the problem of providing symbol synchronization in the receivers of such systems are discussed. A technique is presented for extracting symbol sync from an MASK or QASK signal. The scheme is a generalization of the data transition tracking loop used in PSK systems. The performance of the loop was analyzed in terms of its mean-squared jitter and its effects on the data detection process in MASK and QASK systems.

Motor Synchronization in Patients With Schizophrenia: Preserved Time Representation With Abnormalities in Predictive Timing

Directory of Open Access Journals (Sweden)

Hélène Wilquin

2018-05-01

Full Text Available Objective: Basic temporal dysfunctions have been described in patients with schizophrenia, which may impact their ability to connect and synchronize with the outer world. The present study was conducted with the aim to distinguish between interval timing and synchronization difficulties and more generally the spatial-temporal organization disturbances for voluntary actions. A new sensorimotor synchronization task was developed to test these abilities.Method: Twenty-four chronic schizophrenia patients matched with 27 controls performed a spatial-tapping task in which finger taps were to be produced in synchrony with a regular metronome to six visual targets presented around a virtual circle on a tactile screen. Isochronous (time intervals of 500 ms and non-isochronous auditory sequences (alternated time intervals of 300/600 ms were presented. The capacity to produce time intervals accurately versus the ability to synchronize own actions (tap with external events (tone were measured.Results: Patients with schizophrenia were able to produce the tapping patterns of both isochronous and non-isochronous auditory sequences as accurately as controls producing inter-response intervals close to the expected interval of 500 and 900 ms, respectively. However, the synchronization performances revealed significantly more positive asynchrony means (but similar variances in the patient group than in the control group for both types of auditory sequences.Conclusion: The patterns of results suggest that patients with schizophrenia are able to perceive and produce both simple and complex sequences of time intervals but are impaired in the ability to synchronize their actions with external events. These findings suggest a specific deficit in predictive timing, which may be at the core of early symptoms previously described in schizophrenia.

Online synchronous communication in the second-language classroom

Directory of Open Access Journals (Sweden)

Elizabeth Murphy

2010-07-01

Full Text Available Abstract: The study reported on in this paper used a framework of benefits, challenges and solutions to categorize data from a design experiment using synchronous online communication for learning French as a second language (FSL. Participants were 92 Grade 6, FSL students and four teachers from urban and rural areas of Newfoundland, Canada. Data collection relied on online observation, teachers’ use of blogs and an online discussion forum, face-to-face planning and reflection meetings for teachers as well as interviews with all participants. Benefits included independence and peer-learning; authenticity and motivation; anonymity and confidence; enhanced self-esteem. Challenges related to teacher multi-tasking; poor sound quality; technical problems; momentum; grouping; scheduling. Solutions included use of student moderators; audio tutorials and direct messaging; activity tutorials; technical support and capacity building. The categories and their subcategories were grouped into two themes of positive affect and student-centered learning. Résumé : L’étude décrite dans le présent article a utilisé un cadre prenant en considération les bénéfices, les défis et les solutions afin de classer les données d’un dispositif expérimental utilisant la communication synchrone en ligne pour l’apprentissage du français langue seconde (FLS. Les participants étaient 92 élèves en FLS de sixième année et quatre enseignants de milieux urbains et ruraux de Terre-Neuve, Canada. La collecte des données s’est fondée sur l’observation en ligne, l’utilisation de cybercarnets et d’un forum de discussion en ligne par les enseignants, la planification en face-à-face et des réunions de réflexion pour les enseignants, ainsi que des entrevues avec tous les participants. Les bénéfices comprenaient : l’indépendance et l’apprentissage entre pairs; l’authenticité et la motivation; l’anonymat et la confiance; l�

Using the amplitude variation of a reverberation chamber channel to predict the synchronization of a wireless digital communication test system

NARCIS (Netherlands)

Tanuhardja, Ray R.; Gonzalez, Luis A.; Wang, Chih-Ming; Young, William F.; Remley, Kate A.; Ladbury, John M.

2015-01-01

We discuss the use of a metric based on the amplitude variation of a channel in the signal bandwidth to predict whether or not a digital wireless communication test system receiver will be able to demodulate a test signal. This metric is compared to another method consisting of the correlation

A new type of chaotic synchronization with application to communication systems

International Nuclear Information System (INIS)

Kharel, Rupak; Busawon, Krishna

2011-01-01

In this paper, we propose a new methodology to synchronize a class of chaotic systems starting from different initial conditions under some given conditions. The method we propose is not based on the unidirectional synchronization method like the one proposed by Pecora-Caroll. The proposed method is unique in the sense that the chaotic oscillators to be synchronized have no direct connection between them; that is, there is no signal being sent from one to the other. Simulation result is presented to show the synchronization performance.

Chaos synchronization communication using extremely unsymmetrical bidirectional injections.

Science.gov (United States)

Zhang, Wei Li; Pan, Wei; Luo, Bin; Zou, Xi Hua; Wang, Meng Yao; Zhou, Zhi

2008-02-01

Chaos synchronization and message transmission between two semiconductor lasers with extremely unsymmetrical bidirectional injections (EUBIs) are discussed. By using EUBIs, synchronization is realized through injection locking. Numerical results show that if the laser subjected to strong injection serves as the receiver, chaos pass filtering (CPF) of the system is similar to that of unidirectional coupled systems. Moreover, if the other laser serves as the receiver, a stronger CPF can be obtained. Finally, we demonstrate that messages can be extracted successfully from either of the two transmission directions of the system.

The value of perfusion CT in predicting the short-term response to synchronous radiochemotherapy for cervical squamous cancer

International Nuclear Information System (INIS)

Li, Xiang Sheng; Fan, Hong Xia; Zhu, Hong Xian; Song, Yun Long; Zhou, Chun Wu

2012-01-01

To determine the value of the perfusion parameters in predicting short-term tumour response to synchronous radiochemotherapy for cervical squamous carcinoma. Ninety-three patients with cervical squamous carcinoma later than stage IIB were included in this study. Perfusion CT was performed for all these patients who subsequently received the same synchronous radiochemotherapy. The patients were divided into responders and non-responders according to short-term response to treatment. Baseline perfusion parameters of the two groups were compared. The perfusion parameters that might affect treatment effect were analysed by using a multivariate multi-regression analysis. The responders group had higher baseline permeability-surface area product (PS) and blood volume (BV) values than the non-responders group (P 0.05). At multivariate multi-regression analysis, BV, PS and tumour size were significant factors in the prediction of treatment effect. Small tumours usually had high PS and BV values, and thus had a good treatment response. Perfusion CT can provide some helpful information for the prediction of the short-term effect. Synchronous radiochemotherapy may be more effective in cervical squamous carcinoma with higher baseline PS and BV. (orig.)

Making sense of media synchronicity in humanitarian crises

NARCIS (Netherlands)

Muhren, W.J.; van den Eede, G.G.P.; van de Walle, B.A.

2009-01-01

This paper reintroduces concepts from sensemaking in media synchronicity theory (MST). It focuses on how media should support synchronicity to fit communication needs when making sense of a humanitarian crisis situation. Findings from interviews with senior management of humanitarian aid

Disruption of posteromedial large-scale neural communication predicts recovery from coma.

Science.gov (United States)

Silva, Stein; de Pasquale, Francesco; Vuillaume, Corine; Riu, Beatrice; Loubinoux, Isabelle; Geeraerts, Thomas; Seguin, Thierry; Bounes, Vincent; Fourcade, Olivier; Demonet, Jean-Francois; Péran, Patrice

2015-12-08

We hypothesize that the major consciousness deficit observed in coma is due to the breakdown of long-range neuronal communication supported by precuneus and posterior cingulate cortex (PCC), and that prognosis depends on a specific connectivity pattern in these networks. We compared 27 prospectively recruited comatose patients who had severe brain injury (Glasgow Coma Scale score Coma Recovery Scale-Revised (CRS-R). Patients who were comatose showed a significant disruption of functional connectivity of brain areas spontaneously synchronized with PCC, globally notwithstanding etiology. The functional connectivity strength between PCC and medial prefrontal cortex (mPFC) was significantly different between comatose patients who went on to recover and those who eventually scored an unfavorable outcome 3 months after brain injury (Kruskal-Wallis test, p coma. Sparing of functional connectivity between PCC and mPFC may predict patient outcome, and further studies are needed to substantiate this potential prognosis biomarker. © 2015 American Academy of Neurology.

Analysis of communications and implementation performance of FFT based carrier synchronization of BPSK/QPSK bursts

Directory of Open Access Journals (Sweden)

U. Wasenmüller

2008-05-01

Full Text Available Carrier synchronization is a vital part of every inner receiver in wireless communications. Frequency offset and phase offset of the received burst must be estimated and the received samples must be corrected according to the estimation. An approximation of the maximum likelihood estimation of frequency offset is given by the Fast Fourier Transform (FFT. The accuracy of the estimation as well as the hardware complexity and throughput depend on the number of FFT points. We demonstrate three techniques to improve the accuracy of the FFT based frequency offset estimation respectively to reduce the number of needed FFT points. These three techniques as well as the reference algorithm without improvements combine phase offset estimation with frequency offset estimation. We present the communications and FPGA implementation performance of these techniques.

Detection of generalized synchronization using echo state networks

OpenAIRE

Ibáñez-Soria, D.; García Ojalvo, Jordi; Soria Frisch, Aureli; Ruffini, G.

2018-01-01

Generalized synchronization between coupled dynamical systems is a phenomenon of relevance in applications that range from secure communications to physiological modelling. Here, we test the capabilities of reservoir computing and, in particular, echo state networks for the detection of generalized synchronization. A nonlinear dynamical system consisting of two coupled Rössler chaotic attractors is used to generate temporal series consisting of time-locked generalized synchronized sequences i...

Analytical and Numerical Study of the Projective Synchronization of the Chaotic Complex Nonlinear Systems with Uncertain Parameters and Its Applications in Secure Communication

Directory of Open Access Journals (Sweden)

Kholod M. Abualnaja

2014-01-01

to demonstrate the effectiveness of the proposed synchronization scheme and verify the theoretical results. The above results will provide theoretical foundation for the secure communication applications based on the proposed scheme.

Neural correlates of auditory temporal predictions during sensorimotor synchronization

Directory of Open Access Journals (Sweden)

Nadine ePecenka

2013-08-01

Full Text Available Musical ensemble performance requires temporally precise interpersonal action coordination. To play in synchrony, ensemble musicians presumably rely on anticipatory mechanisms that enable them to predict the timing of sounds produced by co-performers. Previous studies have shown that individuals differ in their ability to predict upcoming tempo changes in paced finger-tapping tasks (indexed by cross-correlations between tap timing and pacing events and that the degree of such prediction influences the accuracy of sensorimotor synchronization (SMS and interpersonal coordination in dyadic tapping tasks. The current functional magnetic resonance imaging study investigated the neural correlates of auditory temporal predictions during SMS in a within-subject design. Hemodynamic responses were recorded from 18 musicians while they tapped in synchrony with auditory sequences containing gradual tempo changes under conditions of varying cognitive load (achieved by a simultaneous visual n-back working-memory task comprising three levels of difficulty: observation only, 1-back, and 2-back object comparisons. Prediction ability during SMS decreased with increasing cognitive load. Results of a parametric analysis revealed that the generation of auditory temporal predictions during SMS recruits (1 a distributed network in cortico-cerebellar motor-related brain areas (left dorsal premotor and motor cortex, right lateral cerebellum, SMA proper and bilateral inferior parietal cortex and (2 medial cortical areas (medial prefrontal cortex, posterior cingulate cortex. While the first network is presumably involved in basic sensory prediction, sensorimotor integration, motor timing, and temporal adaptation, activation in the second set of areas may be related to higher-level social-cognitive processes elicited during action coordination with auditory signals that resemble music performed by human agents.

Permanent synchronization of camcorders via LANC protocol

Science.gov (United States)

Vrancic, Damir; Smith, Steven L.

2006-02-01

A device, which keeps two camcorders permanently in synchronization, has been developed. The mentioned device uses LANC (CONTROL-L) camcorder's inputs for synchronization. It enables controlling of two camcorders simultaneously via built-in buttons, by using external LANC remote controller and/or by the PC via serial (RS232) communication. Since device requires LANC inputs on camcorders or ACC inputs on still cameras, it can be used on some camcorders produced by manufacturers Sony and Canon or some still cameras produced by Sony. The device initially synchronizes camcorders or still cameras by applying arbitrarily delayed power-up pulses on LANC (ACC) inputs. Then, on user demand, the camcorders can be permanently synchronized (valid only for some camcorders produced by Sony). The effectiveness of the proposed device is demonstrated by several experiments on three types of camcorders (DCR-TRV900E, HDR-HC1, HVR-Z1U) and one type of still camera (DSC-V1). The electronic schemes, PCB layouts, firmware and communication programs are freely available (under GPL licence).

Evaluation of global synchronization for iterative algebra algorithms on many-core

KAUST Repository

ul Hasan Khan, Ayaz; Al-Mouhamed, Mayez; Firdaus, Lutfi A.

2015-01-01

© 2015 IEEE. Massively parallel computing is applied extensively in various scientific and engineering domains. With the growing interest in many-core architectures and due to the lack of explicit support for inter-block synchronization specifically in GPUs, synchronization becomes necessary to minimize inter-block communication time. In this paper, we have proposed two new inter-block synchronization techniques: 1) Relaxed Synchronization, and 2) Block-Query Synchronization. These schemes are used in implementing numerical iterative solvers where computation/communication overlapping is one used optimization to enhance application performance. We have evaluated and analyzed the performance of the proposed synchronization techniques using Jacobi Iterative Solver in comparison to the state of the art inter-block lock-free synchronization techniques. We have achieved about 1-8% performance improvement in terms of execution time over lock-free synchronization depending on the problem size and the number of thread blocks. We have also evaluated the proposed algorithm on GPU and MIC architectures and obtained about 8-26% performance improvement over the barrier synchronization available in OpenMP programming environment depending on the problem size and number of cores used.

Evaluation of global synchronization for iterative algebra algorithms on many-core

KAUST Repository

ul Hasan Khan, Ayaz

2015-06-01

© 2015 IEEE. Massively parallel computing is applied extensively in various scientific and engineering domains. With the growing interest in many-core architectures and due to the lack of explicit support for inter-block synchronization specifically in GPUs, synchronization becomes necessary to minimize inter-block communication time. In this paper, we have proposed two new inter-block synchronization techniques: 1) Relaxed Synchronization, and 2) Block-Query Synchronization. These schemes are used in implementing numerical iterative solvers where computation/communication overlapping is one used optimization to enhance application performance. We have evaluated and analyzed the performance of the proposed synchronization techniques using Jacobi Iterative Solver in comparison to the state of the art inter-block lock-free synchronization techniques. We have achieved about 1-8% performance improvement in terms of execution time over lock-free synchronization depending on the problem size and the number of thread blocks. We have also evaluated the proposed algorithm on GPU and MIC architectures and obtained about 8-26% performance improvement over the barrier synchronization available in OpenMP programming environment depending on the problem size and number of cores used.

Enhancing Time Synchronization Support in Wireless Sensor Networks.

Science.gov (United States)

Tavares Bruscato, Leandro; Heimfarth, Tales; Pignaton de Freitas, Edison

2017-12-20

With the emerging Internet of Things (IoT) technology becoming reality, a number of applications are being proposed. Several of these applications are highly dependent on wireless sensor networks (WSN) to acquire data from the surrounding environment. In order to be really useful for most of applications, the acquired data must be coherent in terms of the time in which they are acquired, which implies that the entire sensor network presents a certain level of time synchronization. Moreover, to efficiently exchange and forward data, many communication protocols used in WSN rely also on time synchronization among the sensor nodes. Observing the importance in complying with this need for time synchronization, this work focuses on the second synchronization problem, proposing, implementing and testing a time synchronization service for low-power WSN using low frequency real-time clocks in each node. To implement this service, three algorithms based on different strategies are proposed: one based on an auto-correction approach, the second based on a prediction mechanism, while the third uses an analytical correction mechanism. Their goal is the same, i.e., to make the clocks of the sensor nodes converge as quickly as possible and then to keep them most similar as possible. This goal comes along with the requirement to keep low energy consumption. Differently from other works in the literature, the proposal here is independent of any specific protocol, i.e., it may be adapted to be used in different protocols. Moreover, it explores the minimum number of synchronization messages by means of a smart clock update strategy, allowing the trade-off between the desired level of synchronization and the associated energy consumption. Experimental results, which includes data acquired from simulations and testbed deployments, provide evidence of the success in meeting this goal, as well as providing means to compare these three approaches considering the best synchronization

Enhancing Time Synchronization Support in Wireless Sensor Networks

Science.gov (United States)

Tavares Bruscato, Leandro; Heimfarth, Tales; Pignaton de Freitas, Edison

2017-01-01

With the emerging Internet of Things (IoT) technology becoming reality, a number of applications are being proposed. Several of these applications are highly dependent on wireless sensor networks (WSN) to acquire data from the surrounding environment. In order to be really useful for most of applications, the acquired data must be coherent in terms of the time in which they are acquired, which implies that the entire sensor network presents a certain level of time synchronization. Moreover, to efficiently exchange and forward data, many communication protocols used in WSN rely also on time synchronization among the sensor nodes. Observing the importance in complying with this need for time synchronization, this work focuses on the second synchronization problem, proposing, implementing and testing a time synchronization service for low-power WSN using low frequency real-time clocks in each node. To implement this service, three algorithms based on different strategies are proposed: one based on an auto-correction approach, the second based on a prediction mechanism, while the third uses an analytical correction mechanism. Their goal is the same, i.e., to make the clocks of the sensor nodes converge as quickly as possible and then to keep them most similar as possible. This goal comes along with the requirement to keep low energy consumption. Differently from other works in the literature, the proposal here is independent of any specific protocol, i.e., it may be adapted to be used in different protocols. Moreover, it explores the minimum number of synchronization messages by means of a smart clock update strategy, allowing the trade-off between the desired level of synchronization and the associated energy consumption. Experimental results, which includes data acquired from simulations and testbed deployments, provide evidence of the success in meeting this goal, as well as providing means to compare these three approaches considering the best synchronization

Generating Virtual Eye Contacts Through Online Synchronous Communications in Virtual Classroom Applications

Directory of Open Access Journals (Sweden)

T. Volkan YUZER

2007-01-01

Full Text Available The Internet usage has been increasing among persons in the worldwide. This situation highlights that the number of potential distance learners has been increasing in the Internet society. Besides, the terms and concepts of the Internet environments become to be spread out in this society like virtual reality. It is also possible to explain the characters of the Internet clearly via generating relatively new terms or concepts. “Virtual eye contact” concept is one of these. In this article, this concept is considered with a specific application of synchronous internet-based e-learning environments which is virtual classroom platform application. Explanation, technological infrastructure and benefits of this concept and training of the trainers to use this nonverbal communication type more powerfully are explained and discussed.

Review of available synchronization and time distribution techniques

Science.gov (United States)

Hall, R. G.; Lieberman, T. N.; Stone, R. R.

1974-01-01

The methods of synchronizing precision clocks will be reviewed placing particular attention to the simpler techniques, their accuracies, and the approximate cost of equipment. The more exotic methods of synchronization are discussed in lesser detail. The synchronization techniques that will be covered will include satellite dissemination, communication and navigation transmissions via VLF, LF, HF, UHF and microwave as well as commercial and armed forces television. Portable clock trips will also be discussed.

Synchronization Of Parallel Discrete Event Simulations

Science.gov (United States)

Steinman, Jeffrey S.

1992-01-01

Adaptive, parallel, discrete-event-simulation-synchronization algorithm, Breathing Time Buckets, developed in Synchronous Parallel Environment for Emulation and Discrete Event Simulation (SPEEDES) operating system. Algorithm allows parallel simulations to process events optimistically in fluctuating time cycles that naturally adapt while simulation in progress. Combines best of optimistic and conservative synchronization strategies while avoiding major disadvantages. Algorithm processes events optimistically in time cycles adapting while simulation in progress. Well suited for modeling communication networks, for large-scale war games, for simulated flights of aircraft, for simulations of computer equipment, for mathematical modeling, for interactive engineering simulations, and for depictions of flows of information.

The Effects of a Synchronous Communication Tool (Yahoo Messenger) on Online Learners' Sense of Community and Their Multimedia Authoring Skills

Science.gov (United States)

Wang, Shiang-Kwei

2008-01-01

Literature suggests that developing a community of learners is the key to a successful online-learning experience. In this study, the instructor of a multimedia authoring course adopted a synchronous communication tool (Yahoo Messenger) to interact with learners orally on a weekly basis and, thereby, to establish a sense among the learners that…

Using synchronization in multi-model ensembles to improve prediction

Science.gov (United States)

Hiemstra, P.; Selten, F.

2012-04-01

In recent decades, many climate models have been developed to understand and predict the behavior of the Earth's climate system. Although these models are all based on the same basic physical principles, they still show different behavior. This is for example caused by the choice of how to parametrize sub-grid scale processes. One method to combine these imperfect models, is to run a multi-model ensemble. The models are given identical initial conditions and are integrated forward in time. A multi-model estimate can for example be a weighted mean of the ensemble members. We propose to go a step further, and try to obtain synchronization between the imperfect models by connecting the multi-model ensemble, and exchanging information. The combined multi-model ensemble is also known as a supermodel. The supermodel has learned from observations how to optimally exchange information between the ensemble members. In this study we focused on the density and formulation of the onnections within the supermodel. The main question was whether we could obtain syn-chronization between two climate models when connecting only a subset of their state spaces. Limiting the connected subspace has two advantages: 1) it limits the transfer of data (bytes) between the ensemble, which can be a limiting factor in large scale climate models, and 2) learning the optimal connection strategy from observations is easier. To answer the research question, we connected two identical quasi-geostrohic (QG) atmospheric models to each other, where the model have different initial conditions. The QG model is a qualitatively realistic simulation of the winter flow on the Northern hemisphere, has three layers and uses a spectral imple-mentation. We connected the models in the original spherical harmonical state space, and in linear combinations of these spherical harmonics, i.e. Empirical Orthogonal Functions (EOFs). We show that when connecting through spherical harmonics, we only need to connect 28% of

Switched modified function projective synchronization of hyperchaotic Qi system with uncertain parameters

Science.gov (United States)

Sebastian Sudheer, K.; Sabir, M.

2010-12-01

This work is involved with switched modified function projective synchronization of two identical Qi hyperchaotic systems using adaptive control method. Switched synchronization of chaotic systems in which a state variable of the drive system synchronize with a different state variable of the response system is a promising type of synchronization as it provides greater security in secure communication. Modified function projective synchronization with the unpredictability of scaling functions can enhance security. Recently formulated hyperchaotic Qi system in the hyperchaotic mode has an extremely broad frequency bandwidth of high magnitudes, verifying its unusual random nature and indicating its great potential for some relevant engineering applications such as secure communications. By Lyapunove stability theory, the adaptive control law and the parameter update law are derived to make the state of two chaotic systems modified function projective synchronized. Synchronization under the effect of noise is also considered. Numerical simulations are presented to demonstrate the effectiveness of the proposed adaptive controllers.

Synchronization of complex chaotic systems in series expansion form

International Nuclear Information System (INIS)

Ge Zhengming; Yang Chenghsiung

2007-01-01

This paper studies the synchronization of complex chaotic systems in series expansion form by Lyapunov asymptotical stability theorem. A sufficient condition is given for the asymptotical stability of an error dynamics, and is applied to guiding the design of the secure communication. Finally, numerical results are studied for the Quantum-CNN oscillators synchronizing with unidirectional/bidirectional linear coupling to show the effectiveness of the proposed synchronization strategy

A Spatiotemporal-Chaos-Based Cryptosystem Taking Advantage of Both Synchronous and Self-Synchronizing Schemes

Science.gov (United States)

Lü, Hua-Ping; Wang, Shi-Hong; Li, Xiao-Wen; Tang, Guo-Ning; Kuang, Jin-Yu; Ye, Wei-Ping; Hu, Gang

2004-06-01

Two-dimensional one-way coupled map lattices are used for cryptography where multiple space units produce chaotic outputs in parallel. One of the outputs plays the role of driving for synchronization of the decryption system while the others perform the function of information encoding. With this separation of functions the receiver can establish a self-checking and self-correction mechanism, and enjoys the advantages of both synchronous and self-synchronizing schemes. A comparison between the present system with the system of advanced encryption standard (AES) is presented in the aspect of channel noise influence. Numerical investigations show that our system is much stronger than AES against channel noise perturbations, and thus can be better used for secure communications with large channel noise.

Observer-based hyperchaos synchronization in cascaded discrete-time systems

International Nuclear Information System (INIS)

Grassi, Giuseppe

2009-01-01

This paper deals with the observer-based synchronization in a cascade connection of hyperchaotic discrete-time systems. The paper demonstrates that exact synchronization in finite time is achievable between pairs of drive-response systems using only a scalar synchronizing signal. This 'propagated synchronization' starts from the innermost drive-response system pair and propagates toward the outermost drive-system pair. Choosing the drive-system input to be an information signal (encrypted via an arbitrary encryption function) yields a potential application of this architecture in chaos-based communications.

Mixed synchronization in chaotic oscillators using scalar coupling

Energy Technology Data Exchange (ETDEWEB)

Bhowmick, Sourav K.; Hens, Chittaranjan [CSIR – Indian Institute of Chemical Biology, Jadavpur, Kolkata 700032 (India); Ghosh, Dibakar, E-mail: drghosh_math@yahoo.co.in [Department of Mathematics, University of Kalyani, West Bengal 741235 (India); Dana, Syamal K. [CSIR – Indian Institute of Chemical Biology, Jadavpur, Kolkata 700032 (India)

2012-07-23

We report experimental evidence of mixed synchronization in two unidirectionally coupled chaotic oscillators using a scalar coupling. In this synchronization regime, some of the state variables may be in complete synchronization while others may be in anti-synchronization state. We extended the theory by using an adaptive controller with an updating law based on Lyapunov function stability to include parameter fluctuation. Using the scheme, we implemented a cryptographic encoding for digital signal through parameter modulation. -- Highlights: ► We provided experimental evidence of the mixed synchronization scheme while other methods are mostly theoretical nature. ► We numerically studied adaptive mixed synchronization when the parameters are not completely known using scalar coupling. ► We proposed a secure communication system where three digital messages are transmitted using parameter modulation.

Detection of generalized synchronization using echo state networks

Science.gov (United States)

Ibáñez-Soria, D.; Garcia-Ojalvo, J.; Soria-Frisch, A.; Ruffini, G.

2018-03-01

Generalized synchronization between coupled dynamical systems is a phenomenon of relevance in applications that range from secure communications to physiological modelling. Here, we test the capabilities of reservoir computing and, in particular, echo state networks for the detection of generalized synchronization. A nonlinear dynamical system consisting of two coupled Rössler chaotic attractors is used to generate temporal series consisting of time-locked generalized synchronized sequences interleaved with unsynchronized ones. Correctly tuned, echo state networks are able to efficiently discriminate between unsynchronized and synchronized sequences even in the presence of relatively high levels of noise. Compared to other state-of-the-art techniques of synchronization detection, the online capabilities of the proposed Echo State Network based methodology make it a promising choice for real-time applications aiming to monitor dynamical synchronization changes in continuous signals.

Oral Communication Skills Assessment in a Synchronous Hybrid MBA Programme: Does Attending Face-to-Face Matter for US and International Students?

Science.gov (United States)

Butz, Nikolaus T.; Askim-Lovseth, Mary K.

2015-01-01

The ability to communicate effectively is an essential skill for graduates of Masters of Business Administration (MBA) programmes; however, as synchronous hybrid learning becomes more common, business schools may find it challenging to assess students' proficiency in this core area. An additional layer of complexity is added by the burgeoning…

The Effect of Dynamic Assessment in Synchronous Computer-Mediated Communication on Iranian EFL Learners' Listening Comprehension Ability at Upper-Intermediate Level

Science.gov (United States)

Heidar, Davood Mashhadi; Afghari, Akbar

2015-01-01

The present paper concentrates on a web-based inquiry in the synchronous computer-mediated communication (SCMC) via Web 2.0 technologies of Talk and Write and Skype. It investigates EFL learners' socio-cognitive progress through dynamic assessment (DA), which follows Vygotsky's inclination for supportive interchange in the zone of proximal…

Tutorial chat: a case study of synchronous communication in a learning environment

Directory of Open Access Journals (Sweden)

Malcolm Rutter

2006-12-01

Full Text Available This case study describes the use of a web-based synchronous chat application, run during computing tutorials. The chat room was moderated by a paid demonstrator, who assisted and encouraged students whenever possible. Most of the discussion was banter, which acted as a lubricant for relevant factual communication. Students were permitted a degree of anonymity, but nevertheless learned to treat the facility in a useful manner. The application and its mode of employment were found to be both motivating and supportive. Use was evaluated by questionnaire and an analysis of student input. As a result of the experience, it is suggested that abuse will certainly occur and may be minimised by technical improvements, but never eliminated. The Rogerian approach adopted was found to have transferred emphasis from teaching a topic to the learning of generic skills.

State-based Communication on Time-predictable Multicore Processors

DEFF Research Database (Denmark)

Sørensen, Rasmus Bo; Schoeberl, Martin; Sparsø, Jens

2016-01-01

Some real-time systems use a form of task-to-task communication called state-based or sample-based communication that does not impose any flow control among the communicating tasks. The concept is similar to a shared variable, where a reader may read the same value multiple times or may not read...... a given value at all. This paper explores time-predictable implementations of state-based communication in network-on-chip based multicore platforms through five algorithms. With the presented analysis of the implemented algorithms, the communicating tasks of one core can be scheduled independently...... of tasks on other cores. Assuming a specific time-predictable multicore processor, we evaluate how the read and write primitives of the five algorithms contribute to the worst-case execution time of the communicating tasks. Each of the five algorithms has specific capabilities that make them suitable...

Phenomena of synchronized response in biosystems and the possible mechanism.

Science.gov (United States)

Xu, Jingjing; Yang, Fan; Han, Danhong; Xu, Shengyong

2018-02-05

Phenomena of synchronized response is common among organs, tissues and cells in biosystems. We have analyzed and discussed three examples of synchronization in biosystems, including the direction-changing movement of paramecia, the prey behavior of flytraps, and the simultaneous discharge of electric eels. These phenomena and discussions support an electrical communication mechanism that in biosystems, the electrical signals are mainly soliton-like electromagnetic pulses, which are generated by the transient transmembrane ionic current through the ion channels and propagate along the dielectric membrane-based softmaterial waveguide network to complete synchronized responses. This transmission model implies that a uniform electrical communication mechanism might have been naturally developed in biosystem. Copyright © 2018 Elsevier Inc. All rights reserved.

A secure communication scheme based generalized function projective synchronization of a new 5D hyperchaotic system

International Nuclear Information System (INIS)

Wu, Xiangjun; Fu, Zhengye; Kurths, Jürgen

2015-01-01

In this paper, a new five-dimensional hyperchaotic system is proposed based on the Lü hyperchaotic system. Some of its basic dynamical properties, such as equilibria, Lyapunov exponents, bifurcations and various attractors are investigated. Furthermore, a new secure communication scheme based on generalized function projective synchronization (GFPS) of this hyperchaotic system with an uncertain parameter is presented. The communication scheme is composed of the modulation, the chaotic receiver, the chaotic transmitter and the demodulation. The modulation mechanism is to modulate the message signal into the system parameter. Then the chaotic signals are sent to the receiver via a public channel. In the receiver end, by designing the controllers and the parameter update rule, GFPS between the transmitter and receiver systems is achieved and the unknown parameter is estimated simultaneously. The message signal can be finally recovered by the identified parameter and the corresponding demodulation method. There is no any limitation on the message size. Numerical simulations are performed to show the validity and feasibility of the presented secure communication scheme. (paper)

Learning through synchronous electronic discussion

NARCIS (Netherlands)

Kanselaar, G.; Veerman, A.L.; Andriessen, J.E.B.

2000-01-01

This article reports a study examining university student pairs carrying out an electronic discussion task in a synchronous computer mediated communication (CMC) system (NetMeeting). The purpose of the assignment was to raise students' awareness concerning conceptions that characterise effective

Epidemic Synchronization in Robotic Swarms

DEFF Research Database (Denmark)

Schiøler, Henrik; Nielsen, Jens Frederik Dalsgaard; Ngo, Trung Dung

2009-01-01

Clock synchronization in swarms of networked mobile robots is studied in a probabilistic, epidemic framework. In this setting communication and synchonization is considered to be a randomized process, taking place at unplanned instants of geographical rendezvous between robots. In combination wit...

On projective synchronization of hyperchaotic complex nonlinear systems based on passive theory for secure communications

International Nuclear Information System (INIS)

Mahmoud, Gamal M; Mahmoud, Emad E; Arafa, Ayman A

2013-01-01

In this paper we deal with the projective synchronization (PS) of hyperchaotic complex nonlinear systems and its application in secure communications based on passive theory. The unpredictability of the scaling factor in PS can additionally enhance the security of communications. In this paper, a scheme for secure message transmission is proposed, and we try to transmit more than one large or bounded message from the transmitter to the receiver. The new hyperchaotic complex Lorenz system is employed to encrypt these messages. In the transmitter, the original messages are modulated into its parameter. In the receiver, we assume that the parameter of the receiver system is uncertain. The controllers and corresponding parameter update law are constructed to achieve PS between the transmitter and receiver system with an uncertain parameter, and identify the unknown parameter via passive theory. The original messages can be recovered successfully through some simple operations by the estimated parameter. Numerical results have verified the effectiveness and feasibility of the presented method. (paper)

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

Energy Technology Data Exchange (ETDEWEB)

Ohmacht, Martin

2017-08-15

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

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

Science.gov (United States)

Ohmacht, Martin

2014-09-09

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

Distributed Synchronization Control of Multiagent Systems With Unknown Nonlinearities.

Science.gov (United States)

Su, Shize; Lin, Zongli; Garcia, Alfredo

2016-01-01

This paper revisits the distributed adaptive control problem for synchronization of multiagent systems where the dynamics of the agents are nonlinear, nonidentical, unknown, and subject to external disturbances. Two communication topologies, represented, respectively, by a fixed strongly-connected directed graph and by a switching connected undirected graph, are considered. Under both of these communication topologies, we use distributed neural networks to approximate the uncertain dynamics. Decentralized adaptive control protocols are then constructed to solve the cooperative tracker problem, the problem of synchronization of all follower agents to a leader agent. In particular, we show that, under the proposed decentralized control protocols, the synchronization errors are ultimately bounded, and their ultimate bounds can be reduced arbitrarily by choosing the control parameter appropriately. Simulation study verifies the effectiveness of our proposed protocols.

Current error vector based prediction control of the section winding permanent magnet linear synchronous motor

Energy Technology Data Exchange (ETDEWEB)

Hong Junjie, E-mail: hongjjie@mail.sysu.edu.cn [School of Engineering, Sun Yat-Sen University, Guangzhou 510006 (China); Li Liyi, E-mail: liliyi@hit.edu.cn [Dept. Electrical Engineering, Harbin Institute of Technology, Harbin 150000 (China); Zong Zhijian; Liu Zhongtu [School of Engineering, Sun Yat-Sen University, Guangzhou 510006 (China)

2011-10-15

Highlights: {yields} The structure of the permanent magnet linear synchronous motor (SW-PMLSM) is new. {yields} A new current control method CEVPC is employed in this motor. {yields} The sectional power supply method is different to the others and effective. {yields} The performance gets worse with voltage and current limitations. - Abstract: To include features such as greater thrust density, higher efficiency without reducing the thrust stability, this paper proposes a section winding permanent magnet linear synchronous motor (SW-PMLSM), whose iron core is continuous, whereas winding is divided. The discrete system model of the motor is derived. With the definition of the current error vector and selection of the value function, the theory of the current error vector based prediction control (CEVPC) for the motor currents is explained clearly. According to the winding section feature, the motion region of the mover is divided into five zones, in which the implementation of the current predictive control method is proposed. Finally, the experimental platform is constructed and experiments are carried out. The results show: the current control effect has good dynamic response, and the thrust on the mover remains constant basically.

Robust adaptive synchronization of general dynamical networks ...

Indian Academy of Sciences (India)

Robust adaptive synchronization; dynamical network; multiple delays; multiple uncertainties. ... Networks such as neural networks, communication transmission networks, social rela- tionship networks etc. ..... a very good effect. Pramana – J.

System and method for time synchronization in a wireless network

Science.gov (United States)

Gonia, Patrick S.; Kolavennu, Soumitri N.; Mahasenan, Arun V.; Budampati, Ramakrishna S.

2010-03-30

A system includes multiple wireless nodes forming a cluster in a wireless network, where each wireless node is configured to communicate and exchange data wirelessly based on a clock. One of the wireless nodes is configured to operate as a cluster master. Each of the other wireless nodes is configured to (i) receive time synchronization information from a parent node, (ii) adjust its clock based on the received time synchronization information, and (iii) broadcast time synchronization information based on the time synchronization information received by that wireless node. The time synchronization information received by each of the other wireless nodes is based on time synchronization information provided by the cluster master so that the other wireless nodes substantially synchronize their clocks with the clock of the cluster master.

High Speed Frame Synchronization and Viterbi Decoding

DEFF Research Database (Denmark)

Paaske, Erik; Justesen, Jørn; Larsen, Knud J.

1996-01-01

The purpose of Phase 1 of the study is to describe the system structure and algorithms in sufficient detail to allow drawing the high level architecture of units containing frame synchronization and Viterbi decoding. The systems we consider are high data rate space communication systems. Also...... components. Node synchronization performed within a Viterbi decoder is discussed, and algorithms for frame synchronization are described and analyzed. We present a list of system configurations that we find potentially useful. Further, the high level architecture of units that contain frame synchronization...... and various other functions needed in a complete system is presented. Two such units are described, one for placement before the Viterbi decoder and another for placement after the decoder. The high level architectures of three possible implementations of Viterbi decoders are described: The first...

Sensitivity, specificity, predictive value and accuracy of ultrasonography in pregnancy rate prediction in Sahelian goats after progesterone impregnated sponge synchronization

Directory of Open Access Journals (Sweden)

Justin Kouamo

2014-09-01

Full Text Available Aim: This study was aimed to evaluate the sensitivity, specificity, predictive value and accuracy of ultrasonography in pregnancy rate (PR prediction in Sahelian goats after progesterone impregnated sponge synchronization within the framework of caprine artificial insemination (AI program in Fatick (Senegal. Materials and Methods: Of 193 candidate goats in AI program, 167 were selected (day 50 in six villages. Estrus was synchronized by progesterone impregnated sponges installed for 11 days. Two days before the time of sponge removal (day 4, each goat was treated with 500 IU of equine chorionic gonadotropin and 50 μg of dcloprostenol. All goats were inseminated (day 0 with alpine goat semen from France at 45±3 h after sponge removal (day 2. Real-time B-mode ultrasonography was performed at day 50, day 13, day 0, day 40 and day 60 post-AI. Results: Selection rate, estrus response rate, AI rate, PR at days 40 and days 60 were 86.53%; 71.85%; 83.34%; 51% and 68% (p<0.05 respectively. Value of sensitivity, specificity, positive and negative predictive value, accuracy, total conformity, conformity of correct positive, conformity of correct negative and discordance of pregnancy diagnosis by trans-abdominal ultrasonography (TU were 98.03%; 63.26%; 73.52%; 3.12%; 81%; 81%; 50%; 31% and 19%, respectively. Conclusion: These results indicate that the TU can be performed in goats under traditional condition and emphasized the importance of re-examination of goats with negative or doubtful TU diagnoses performed at day 40 post-AI.

The Role of Synchronous Virtual Reference in Teaching and Learning: A Grounded Theory Analysis of Instant Messaging Transcripts

Science.gov (United States)

Passonneau, Sarah; Coffey, Dan

2011-01-01

Electronic communication technologies continue to change the landscape of reference services. For many users, virtual communication is the preferred means of conversing. Synchronous virtual reference, similar to other synchronous means of communication, is an important method for reaching students and for providing teaching and learning…

Special Section on Synchronization in Nonlinear Science and Engineering

Science.gov (United States)

Ikeguchi, Tohru; Tokuda, Isao

Synchronization is a ubiquitous phenomenon of coupled nonlinear oscillators, commonly found in physics, engineering, biology, and other diverse disciplines. It has a long research history back to Christiaan Huygens, who discovered synchronized motion of two pendulum clocks in 1673. It is very easy to observe synchronization in our daily life: e.g., metronomes, candle fires, pet-bottle oscillators, saltwater oscillators, and so on(See, for example, experimental movies at http://www.youtube.com/user/IkeguchiLab?feature=watch). For the last few decades, significant development has been made from both theories and experiments on synchronization of coupled limit cycle oscillators as well as coupled chaotic oscillators. Applications have been also developed to communication technologies, controlling techniques, and data analysis. Combined with the idea from complex network theory, neuroscience, and systems biology, the research speed of synchronization has been even accelerated. This Special Section of NOLTA is primarily dedicated to the recent advanced development of basics and applications of synchronization in science and engineering. A number of qualified works is included, ranging from experimental study on synchronization of Huygens' system, analog circuits, and singing voice to applied study of synchronization in communication networks. One invited paper is devoted to comprehensive reviews on generalized synchronization of chaotic oscillators. On behalf of the editorial committee of the special section, the guest editors would like to express their sincere thanks to all the authors for their excellent contributions. In particular, they are grateful to Prof. Dr. Ulrich Parlitz for contributing his distinguished review article. They would also like to thank the reviewers and the members of the guest editorial committee, especially Prof. Hiroo Sekiya of Chiba University and the editorial staffs of the NOLTA journal, for their supports on publishing this Special

Social Motor Synchronization: Insights for Understanding Social Behavior in Autism.

Science.gov (United States)

Fitzpatrick, Paula; Romero, Veronica; Amaral, Joseph L; Duncan, Amie; Barnard, Holly; Richardson, Michael J; Schmidt, R C

2017-07-01

Impairments in social interaction and communication are critical features of ASD but the underlying processes are poorly understood. An under-explored area is the social motor synchronization that happens when we coordinate our bodies with others. Here, we explored the relationships between dynamical measures of social motor synchronization and assessments of ASD traits. We found (a) spontaneous social motor synchronization was associated with responding to joint attention, cooperation, and theory of mind while intentional social motor synchronization was associated with initiating joint attention and theory of mind; and (b) social motor synchronization was associated with ASD severity but not fully explained by motor problems. Findings suggest that objective measures of social motor synchronization may provide insights into understanding ASD traits.

Asynchronous and Synchronous Online Discussion: Real and Perceived Achievement Differences

Science.gov (United States)

Johnson, Genevieve Marie; Buck, George H.

2007-01-01

Students in an introductory educational psychology course used two WebCT communication tools (synchronous chat and asynchronous discussion) to discuss four case studies. In response to the item, "I learned the case studies best when using," 39 students selected synchronous chat and 51 students selected asynchronous discussion. Students who…

A Synchronous Multi-Body Sensor Platform in a Wireless Body Sensor Network: Design and Implementation

Science.gov (United States)

Gil, Yeongjoon; Wu, Wanqing; Lee, Jungtae

2012-01-01

Background Human life can be further improved if diseases and disorders can be predicted before they become dangerous, by correctly recognizing signals from the human body, so in order to make disease detection more precise, various body-signals need to be measured simultaneously in a synchronized manner. Object This research aims at developing an integrated system for measuring four signals (EEG, ECG, respiration, and PPG) and simultaneously producing synchronous signals on a Wireless Body Sensor Network. Design We designed and implemented a platform for multiple bio-signals using Bluetooth communication. Results First, we developed a prototype board and verified the signals from the sensor platform using frequency responses and quantities. Next, we designed and implemented a lightweight, ultra-compact, low cost, low power-consumption Printed Circuit Board. Conclusion A synchronous multi-body sensor platform is expected to be very useful in telemedicine and emergency rescue scenarios. Furthermore, this system is expected to be able to analyze the mutual effects among body signals. PMID:23112605

A Synchronous Multi-Body Sensor Platform in a Wireless Body Sensor Network: Design and Implementation

Directory of Open Access Journals (Sweden)

Jungtae Lee

2012-07-01

Full Text Available Background: Human life can be further improved if diseases and disorders can be predicted before they become dangerous, by correctly recognizing signals from the human body, so in order to make disease detection more precise, various body-signals need to be measured simultaneously in a synchronized manner. Object: This research aims at developing an integrated system for measuring four signals (EEG, ECG, respiration, and PPG and simultaneously producing synchronous signals on a Wireless Body Sensor Network. Design: We designed and implemented a platform for multiple bio-signals using Bluetooth communication. Results: First, we developed a prototype board and verified the signals from the sensor platform using frequency responses and quantities. Next, we designed and implemented a lightweight, ultra-compact, low cost, low power-consumption Printed Circuit Board. Conclusion: A synchronous multi-body sensor platform is expected to be very useful in telemedicine and emergency rescue scenarios. Furthermore, this system is expected to be able to analyze the mutual effects among body signals.

Synchronicity from Synchronized Chaos

Directory of Open Access Journals (Sweden)

Gregory S. Duane

2015-03-01

Full Text Available The synchronization of loosely-coupled chaotic oscillators, a phenomenon investigated intensively for the last two decades, may realize the philosophical concept of “synchronicity”—the commonplace notion that related eventsmysteriously occur at the same time. When extended to continuous media and/or large discrete arrays, and when general (non-identical correspondences are considered between states, intermittent synchronous relationships indeed become ubiquitous. Meaningful synchronicity follows naturally if meaningful events are identified with coherent structures, defined by internal synchronization between remote degrees of freedom; a condition that has been posited as necessary for synchronizability with an external system. The important case of synchronization between mind and matter is realized if mind is analogized to a computer model, synchronizing with a sporadically observed system, as in meteorological data assimilation. Evidence for the ubiquity of synchronization is reviewed along with recent proposals that: (1 synchronization of different models of the same objective process may be an expeditious route to improved computational modeling and may also describe the functioning of conscious brains; and (2 the nonlocality in quantum phenomena implied by Bell’s theorem may be explained in a variety of deterministic (hidden variable interpretations if the quantum world resides on a generalized synchronization “manifold”.

Synchronicity, instant messaging, and performance among financial traders.

Science.gov (United States)

Saavedra, Serguei; Hagerty, Kathleen; Uzzi, Brian

2011-03-29

Successful animal systems often manage risk through synchronous behavior that spontaneously arises without leadership. In critical human systems facing risk, such as financial markets or military operations, our understanding of the benefits associated with synchronicity is nascent but promising. Building on previous work illuminating commonalities between ecological and human systems, we compare the activity patterns of individual financial traders with the simultaneous activity of other traders--an individual and spontaneous characteristic we call synchronous trading. Additionally, we examine the association of synchronous trading with individual performance and communication patterns. Analyzing empirical data on day traders' second-to-second trading and instant messaging, we find that the higher the traders' synchronous trading is, the less likely they are to lose money at the end of the day. We also find that the daily instant messaging patterns of traders are closely associated with their level of synchronous trading. This result suggests that synchronicity and vanguard technology may help traders cope with risky decisions in complex systems and may furnish unique prospects for achieving collective and individual goals.

Synchronization in Quantum Key Distribution Systems

Directory of Open Access Journals (Sweden)

Anton Pljonkin

2017-10-01

Full Text Available In the description of quantum key distribution systems, much attention is paid to the operation of quantum cryptography protocols. The main problem is the insufficient study of the synchronization process of quantum key distribution systems. This paper contains a general description of quantum cryptography principles. A two-line fiber-optic quantum key distribution system with phase coding of photon states in transceiver and coding station synchronization mode was examined. A quantum key distribution system was built on the basis of the scheme with automatic compensation of polarization mode distortions. Single-photon avalanche diodes were used as optical radiation detecting devices. It was estimated how the parameters used in quantum key distribution systems of optical detectors affect the detection of the time frame with attenuated optical pulse in synchronization mode with respect to its probabilistic and time-domain characteristics. A design method was given for the process that detects the time frame that includes an optical pulse during synchronization. This paper describes the main quantum communication channel attack methods by removing a portion of optical emission. This paper describes the developed synchronization algorithm that takes into account the time required to restore the photodetector’s operation state after the photon has been registered during synchronization. The computer simulation results of the developed synchronization algorithm were analyzed. The efficiency of the developed algorithm with respect to synchronization process protection from unauthorized gathering of optical emission is demonstrated herein.

Adaptive Synchronization between Two Different Complex Networks with Time-Varying Delay Coupling

International Nuclear Information System (INIS)

Jian-Rui, Chen; Li-Cheng, Jiao; Jian-She, Wu; Xiao-Hua, Wang

2009-01-01

A new general network model for two complex networks with time-varying delay coupling is presented. Then we investigate its synchronization phenomena. The two complex networks of the model differ in dynamic nodes, the number of nodes and the coupling connections. By using adaptive controllers, a synchronization criterion is derived. Numerical examples are given to demonstrate the effectiveness of the obtained synchronization criterion. This study may widen the application range of synchronization, such as in chaotic secure communication. (general)

Design and Numerical Simulation of Unidirectional Chaotic Synchronization and its Application in Secure Communication System

Directory of Open Access Journals (Sweden)

A. Sambas

2013-09-01

Full Text Available Chaotic systems are characterized by sensitive dependence on initial conditions, similar to random behavior, and continuous broad-band power spectrum. Chaos is a good potential to be used in secure communications system. In this paper, in order to show some interesting phenomena of three-order Jerk circuit with modulus nonlinearity, the chaotic behavior as a function of a variable control parameter, has been studied. The initial study in this paper is to analyze the phase portraits, the Poincaré maps, the bifurcation diagrams, while the analysis of the synchronization in the case of unidirectional coupling between two identical generated chaotic systems, has been presented. Moreover, some appropriate comparisons are made to contrast some of the existing results. Finally, the effectiveness of the unidirectional coupling scheme between two identical Jerk circuits in a secure communication system is presented in details. Integration of theoretical physics, the numerical simulation by using MATLAB 2010, as well as the implementation of circuit simulations by using MultiSIM 10.0 has been performed in this study

Structural damage detection robust against time synchronization errors

International Nuclear Information System (INIS)

Yan, Guirong; Dyke, Shirley J

2010-01-01

Structural damage detection based on wireless sensor networks can be affected significantly by time synchronization errors among sensors. Precise time synchronization of sensor nodes has been viewed as crucial for addressing this issue. However, precise time synchronization over a long period of time is often impractical in large wireless sensor networks due to two inherent challenges. First, time synchronization needs to be performed periodically, requiring frequent wireless communication among sensors at significant energy cost. Second, significant time synchronization errors may result from node failures which are likely to occur during long-term deployment over civil infrastructures. In this paper, a damage detection approach is proposed that is robust against time synchronization errors in wireless sensor networks. The paper first examines the ways in which time synchronization errors distort identified mode shapes, and then proposes a strategy for reducing distortion in the identified mode shapes. Modified values for these identified mode shapes are then used in conjunction with flexibility-based damage detection methods to localize damage. This alternative approach relaxes the need for frequent sensor synchronization and can tolerate significant time synchronization errors caused by node failures. The proposed approach is successfully demonstrated through numerical simulations and experimental tests in a lab

Theta coupling between V4 and prefrontal cortex predicts visual short-term memory performance.

Science.gov (United States)

Liebe, Stefanie; Hoerzer, Gregor M; Logothetis, Nikos K; Rainer, Gregor

2012-01-29

Short-term memory requires communication between multiple brain regions that collectively mediate the encoding and maintenance of sensory information. It has been suggested that oscillatory synchronization underlies intercortical communication. Yet, whether and how distant cortical areas cooperate during visual memory remains elusive. We examined neural interactions between visual area V4 and the lateral prefrontal cortex using simultaneous local field potential (LFP) recordings and single-unit activity (SUA) in monkeys performing a visual short-term memory task. During the memory period, we observed enhanced between-area phase synchronization in theta frequencies (3-9 Hz) of LFPs together with elevated phase locking of SUA to theta oscillations across regions. In addition, we found that the strength of intercortical locking was predictive of the animals' behavioral performance. This suggests that theta-band synchronization coordinates action potential communication between V4 and prefrontal cortex that may contribute to the maintenance of visual short-term memories.

Comparing Synchronous Virtual Classrooms: Student, Instructor and Course Designer Perspectives

Science.gov (United States)

Lavolette, Elizabeth; Venable, Melissa A.; Gose, Eddie; Huang, Eric

2010-01-01

The synchronous tool that is right for developing an online course depends on the context, needs and priorities. This report compares synchronous, virtual classroom systems Elluminate Live! v. 9 and Dimdim v. 4.5. The researchers compared the features of each system in terms of facilitation of communication, presentation of course content and…

Social and Virtual Networks: Evaluating Synchronous Online Interviewing Using Instant Messenger

Science.gov (United States)

Hinchcliffe, Vanessa; Gavin, Helen

2009-01-01

This paper describes an evaluation of the quality and utility of synchronous online interviewing for data collection in social network research. Synchronous online interviews facilitated by Instant Messenger as the communication medium, were undertaken with ten final year university students. Quantitative and qualitative content analysis of…

Interplay of delay and multiplexing: Impact on cluster synchronization

Science.gov (United States)

Singh, Aradhana; Jalan, Sarika; Boccaletti, Stefano

2017-04-01

Communication delays and multiplexing are ubiquitous features of real-world network systems. We here introduce a simple model where these two features are simultaneously present and report the rich phenomenology which is actually due to their interplay on cluster synchronization. A delay in one layer has non trivial impacts on the collective dynamics of the other layers, enhancing or suppressing synchronization. At the same time, multiplexing may also enhance cluster synchronization of delayed layers. We elucidate several nontrivial (and anti-intuitive) scenarios, which are of interest and potential application in various real-world systems, where the introduction of a delay may render synchronization of a layer robust against changes in the properties of the other layers.

Adaptive projective synchronization between different chaotic ...

Indian Academy of Sciences (India)

Numerical simulation results are performed to explain the effectiveness and feasibility of ... analysis of nonlinear dynamics have gained immense popularity during the last few ... applications of projective synchronization is in secure communication [31] due to ... of uncertain chaotic systems using adaptive control method.

Symplectic Synchronization of Lorenz-Stenflo System with Uncertain Chaotic Parameters via Adaptive Control

Directory of Open Access Journals (Sweden)

Cheng-Hsiung Yang

2013-01-01

Full Text Available A new symplectic chaos synchronization of chaotic systems with uncertain chaotic parameters is studied. The traditional chaos synchronizations are special cases of the symplectic chaos synchronization. A sufficient condition is given for the asymptotical stability of the null solution of error dynamics and a parameter difference. The symplectic chaos synchronization with uncertain chaotic parameters may be applied to the design of secure communication systems. Finally, numerical results are studied for symplectic chaos synchronized from two identical Lorenz-Stenflo systems in three different cases.

Robust chaos synchronization based on adaptive fuzzy delayed ...

Indian Academy of Sciences (India)

cations in secure communication, economics, signal generator design, chemical reaction, ... that may cause instability and poor performance. ... synchronization error system is asymptotically stable with a guaranteed H∞ norm bound.

Estimating parameters of chaotic systems synchronized by external driving signal

International Nuclear Information System (INIS)

Wu Xiaogang; Wang Zuxi

2007-01-01

Noise-induced synchronization (NIS) has evoked great research interests recently. Two uncoupled identical chaotic systems can achieve complete synchronization (CS) by feeding a common noise with appropriate intensity. Actually, NIS belongs to the category of external feedback control (EFC). The significance of applying EFC in secure communication lies in fact that the trajectory of chaotic systems is disturbed so strongly by external driving signal that phase space reconstruction attack fails. In this paper, however, we propose an approach that can accurately estimate the parameters of the chaotic systems synchronized by external driving signal through chaotic transmitted signal, driving signal and their derivatives. Numerical simulation indicates that this approach can estimate system parameters and external coupling strength under two driving modes in a very rapid manner, which implies that EFC is not superior to other methods in secure communication

Epidemic Synchronization in Robotic Swarms

DEFF Research Database (Denmark)

Schiøler, Henrik; Nielsen, Jens Frederik Dalsgaard; Ngo, Trung Dung

2009-01-01

Clock synchronization in swarms of networked mobile robots is studied in a probabilistic, epidemic framework. In this setting communication and synchonization is considered to be a randomized process, taking place at unplanned instants of geographical rendezvous between robots. In combination...... as an infinite-dimensional optimal controlproblem. Illustrative numerical examples are given and commented....

Effects of Synchronous Computer-Mediated Communication and Face-to-Face Interaction on Speaking Skill Development of Iranian EFL Learners

Directory of Open Access Journals (Sweden)

Hakimeh Shahrokhi Mehr

2013-09-01

Full Text Available The traditional form of teaching speaking skill has been via face-to-face (FTF interaction in the classroom setting. Today in the computer age, the on-line forum can provide a virtual environment for differential communication. The pedagogical system benefits from such technology improvement for teaching foreign languages. This quasi-experimental research aimed at comparing the effects of two instructional strategies: synchronous computer-mediated communication (SCMC and FTF interaction. For this purpose, 60 EFL learners were selected from a private language institute as the control (n=30 and experimental (n=30 groups. A speaking test, designed by Hughes (2003, was administered as pretest and after a 12-session treatment the same test was administered as the posttest. The result obtained showed that participants taught based on SCMC fared better than those that were taught according to FTF interaction. Based on the findings of the current study, it is recommended that EFL teachers incorporate computer-mediated communication into their pedagogical procedures.

Online communication predicts Belgian adolescents' initiation of romantic and sexual activity.

Science.gov (United States)

Vandenbosch, Laura; Beyens, Ine; Vangeel, Laurens; Eggermont, Steven

2016-04-01

Online communication is associated with offline romantic and sexual activity among college students. Yet, it is unknown whether online communication is associated with the initiation of romantic and sexual activity among adolescents. This two-wave panel study investigated whether chatting, visiting dating websites, and visiting erotic contact websites predicted adolescents' initiation of romantic and sexual activity. We analyzed two-wave panel data from 1163 Belgian adolescents who participated in the MORES Study. We investigated the longitudinal impact of online communication on the initiation of romantic relationships and sexual intercourse using logistic regression analyses. The odds ratios of initiating a romantic relationship among romantically inexperienced adolescents who frequently used chat rooms, dating websites, or erotic contact websites were two to three times larger than those of non-users. Among sexually inexperienced adolescents who frequently used chat rooms, dating websites, or erotic contact websites, the odds ratios of initiating sexual intercourse were two to five times larger than that among non-users, even after a number of other relevant factors were introduced. This is the first study to demonstrate that online communication predicts the initiation of offline sexual and romantic activity as early as adolescence. Practitioners and parents need to consider the role of online communication in adolescents' developing sexuality. • Adolescents increasingly communicate online with peers. • Online communication predicts romantic and sexual activity among college students. What is New: • Online communication predicts adolescents' offline romantic activity over time. • Online communication predicts adolescents' offline sexual activity over time.

Long distance synchronization of mobile robots

NARCIS (Netherlands)

Alvarez Aguirre, A.; Nijmeijer, H.; Oguchi, T.

2010-01-01

This paper considers the long distance master-slave and mutual synchronization of unicycle-type mobile robots. The issues that arise when the elements of a robotic network are placed in different locations are addressed, specifically the time-delay induced by the communication channel linking the

Implementing a memristive Van der Pol oscillator coupled to a linear oscillator: synchronization and application to secure communication

International Nuclear Information System (INIS)

Megam Ngouonkadi, E B; Fotsin, H B; Louodop Fotso, P

2014-01-01

This paper investigates the dynamics of a memristor-based Van der Pol oscillator coupled to a linear circuit (VDPCL). This chaotic oscillator is a modification of the classical Van der Pol coupled to a linear circuit, and is obtained by replacing the classical cubic nonlinearity by the memristive one. The memristive VDPCL oscillator, in addition to having a very special stability property, exhibits interesting spectral characteristics, which makes it suitable for chaos-based secure communication applications. The memristor is realized by using off-the-shelf components. The basic properties of the circuit are analyzed by means of bifurcation analysis. Chaotic attractors from numerical and experimental analysis are presented, followed by a comparison of results obtained from the modified VDPCL oscillator and those from the classical VDPCL oscillator. An application to synchronization and chaos secure communication is also presented. (paper)

Digital communication system

Science.gov (United States)

Monford, L. G., Jr. (Inventor)

1974-01-01

A digital communication system is reported for parallel operation of 16 or more transceiver units with the use of only four interconnecting wires. A remote synchronization circuit produces unit address control words sequentially in data frames of 16 words. Means are provided in each transceiver unit to decode calling signals and to transmit calling and data signals. The transceivers communicate with each other over one data line. The synchronization unit communicates the address control information to the transceiver units over an address line and further provides the timing information over a clock line. A reference voltage level or ground line completes the interconnecting four wire hookup.

Synchronization of delayed systems in the presence of delay time modulation

International Nuclear Information System (INIS)

Kye, Won-Ho; Choi, Muhan; Kim, Myung-Woon; Lee, Soo-Young; Rim, Sunghwan; Kim, Chil-Min; Park, Young-Jai

2004-01-01

We investigate synchronization in the presence of delay time modulation for application to communication. We have observed that the robust synchronization is established by a common delay signal and its threshold is presented using Lyapunov exponents analysis. The influence of the delay time modulation in chaotic oscillators is also discussed

On the Expressiveness of Intensional Communication

Directory of Open Access Journals (Sweden)

Thomas Given-Wilson

2014-08-01

Full Text Available The expressiveness of communication primitives has been explored in a common framework based on the pi-calculus by considering four features: synchronism (asynchronous vs synchronous, arity (monadic vs polyadic data, communication medium (shared dataspaces vs channel-based, and pattern-matching (binding to a name vs testing name equality. Here pattern-matching is generalised to account for terms with internal structure such as in recent calculi like Spi calculi, Concurrent Pattern Calculus and Psi calculi. This paper explores intensionality upon terms, in particular communication primitives that can match upon both names and structures. By means of possibility/impossibility of encodings, this paper shows that intensionality alone can encode synchronism, arity, communication-medium, and pattern-matching, yet no combination of these without intensionality can encode any intensional language.

Design requirements of communication architecture of SMART safety system

International Nuclear Information System (INIS)

Park, H. Y.; Kim, D. H.; Sin, Y. C.; Lee, J. Y.

2001-01-01

To develop the communication network architecture of safety system of SMART, the evaluation elements for reliability and performance factors are extracted from commercial networks and classified the required-level by importance. A predictable determinacy, status and fixed based architecture, separation and isolation from other systems, high reliability, verification and validation are introduced as the essential requirements of safety system communication network. Based on the suggested requirements, optical cable, star topology, synchronous transmission, point-to-point physical link, connection-oriented logical link, MAC (medium access control) with fixed allocation are selected as the design elements. The proposed architecture will be applied as basic communication network architecture of SMART safety system

Simultaneous Wireless Power Transfer and Data Communication Using Synchronous Pulse-Controlled Load Modulation.

Science.gov (United States)

Mao, Shitong; Wang, Hao; Zhu, Chunbo; Mao, Zhi-Hong; Sun, Mingui

2017-10-01

Wireless Power Transfer (WPT) and wireless data communication are both important problems of research with various applications, especially in medicine. However, these two problems are usually studied separately. In this work, we present a joint study of both problems. Most medical electronic devices, such as smart implants, must have both a power supply to allow continuous operation and a communication link to pass information. Traditionally, separate wireless channels for power transfer and communication are utilized, which complicate the system structure, increase power consumption and make device miniaturization difficult. A more effective approach is to use a single wireless link with both functions of delivering power and passing information. We present a design of such a wireless link in which power and data travel in opposite directions. In order to aggressively miniaturize the implant and reduce power consumption, we eliminate the traditional multi-bit Analog-to-Digital Converter (ADC), digital memory and data transmission circuits all together. Instead, we use a pulse stream, which is obtained from the original biological signal, by a sigma-delta converter and an edge detector, to alter the load properties of the WPT channel. The resulting WPT signal is synchronized with the load changes therefore requiring no memory elements to record inter-pulse intervals. We take advantage of the high sensitivity of the resonant WPT to the load change, and the system dynamic response is used to transfer each pulse. The transient time of the WPT system is analyzed using the coupling mode theory (CMT). Our experimental results show that the memoryless approach works well for both power delivery and data transmission, providing a new wireless platform for the design of future miniaturized medical implants.

Complete and phase synchronization in a heterogeneous small-world neuronal network

International Nuclear Information System (INIS)

Fang, Han; Qi-Shao, Lu; Quan-Bao, Ji; Marian, Wiercigroch

2009-01-01

Synchronous firing of neurons is thought to be important for information communication in neuronal networks. This paper investigates the complete and phase synchronization in a heterogeneous small-world chaotic Hindmarsh–Rose neuronal network. The effects of various network parameters on synchronization behaviour are discussed with some biological explanations. Complete synchronization of small-world neuronal networks is studied theoretically by the master stability function method. It is shown that the coupling strength necessary for complete or phase synchronization decreases with the neuron number, the node degree and the connection density are increased. The effect of heterogeneity of neuronal networks is also considered and it is found that the network heterogeneity has an adverse effect on synchrony. (general)

Balancing Contention and Synchronization on the Intel Paragon

Science.gov (United States)

Bokhari, Shahid H.; Nicol, David M.

1996-01-01

The Intel Paragon is a mesh-connected distributed memory parallel computer. It uses an oblivious and deterministic message routing algorithm: this permits us to develop highly optimized schedules for frequently needed communication patterns. The complete exchange is one such pattern. Several approaches are available for carrying it out on the mesh. We study an algorithm developed by Scott. This algorithm assumes that a communication link can carry one message at a time and that a node can only transmit one message at a time. It requires global synchronization to enforce a schedule of transmissions. Unfortunately global synchronization has substantial overhead on the Paragon. At the same time the powerful interconnection mechanism of this machine permits 2 or 3 messages to share a communication link with minor overhead. It can also overlap multiple message transmission from the same node to some extent. We develop a generalization of Scott's algorithm that executes complete exchange with a prescribed contention. Schedules that incur greater contention require fewer synchronization steps. This permits us to tradeoff contention against synchronization overhead. We describe the performance of this algorithm and compare it with Scott's original algorithm as well as with a naive algorithm that does not take interconnection structure into account. The Bounded contention algorithm is always better than Scott's algorithm and outperforms the naive algorithm for all but the smallest message sizes. The naive algorithm fails to work on meshes larger than 12 x 12. These results show that due consideration of processor interconnect and machine performance parameters is necessary to obtain peak performance from the Paragon and its successor mesh machines.

Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system

International Nuclear Information System (INIS)

Messadi, Manal; Mellit, Adel; Kemih, Karim; Ghanes, Malek

2015-01-01

This paper investigates how to address the chaos problem in a permanent magnet synchronous generator (PMSG) in a wind turbine system. Predictive control approach is proposed to suppress chaotic behavior and make operating stable; the advantage of this method is that it can only be applied to one state of the wind turbine system. The use of the genetic algorithms to estimate the optimal parameter values of the wind turbine leads to maximization of the power generation. Moreover, some simulation results are included to visualize the effectiveness and robustness of the proposed method. (paper)

Organization of synchronization of power supplies for the T-15 device injector

International Nuclear Information System (INIS)

Gerasimov, V.P.; Gordin, V.I.; Grachev, V.F.; Ishkin, V.A.; Mozin, I.V.; Kuz'min, B.N.; Skosarev, V.A.

1984-01-01

The description of the system for the T-15 tokamak power supply and injector synchronization is presented. The synchronization system consists of 3 branches, comprising 6 sychronization devices according to the number of ion sources. According to the character of control, structurally and territorially, each branch of the synchronization system is devided into three parts: program-controlled, relized in CAMAC standard, synchronization devices, located in the room of low-voltage power supply system, and control channels, manufactured in the form of optical communication channels with controls units or galvanic decoupling units

Satellite Communications

Indian Academy of Sciences (India)

First page Back Continue Last page Overview Graphics. Satellite Communications. Arthur C Clarke wrote a seminal paper in 1945 in wireless world. Use three satellites in geo-synchronous orbit to enable intercontinental communications. System could be realised in '50 to 100 years'

Langevin approach to synchronization of hyperchaotic time-delay dynamics

Energy Technology Data Exchange (ETDEWEB)

Budini, Adrian A [Consejo Nacional de Investigaciones CientIficas y Tecnicas, Centro Atomico Bariloche, Av. E Bustillo Km 9.5, (8400) Bariloche (Argentina); Consortium of the Americas for Interdisciplinary Science and Department of Physics and Astronomy, University of New Mexico, Albuquerque, NM 87131 (United States)

2008-11-07

In this paper, we characterize the synchronization phenomenon of hyperchaotic scalar nonlinear delay dynamics in a fully-developed chaos regime. Our results rely on the observation that, in that regime, the stationary statistical properties of a class of hyperchaotic attractors can be reproduced with a linear Langevin equation, defined by replacing the nonlinear delay force by a delta-correlated noise. Therefore, the synchronization phenomenon can be analytically characterized by a set of coupled Langevin equations. We apply this formalism to study anticipated synchronization dynamics subject to external noise fluctuations as well as for characterizing the effects of parameter mismatch in a hyperchaotic communication scheme. The same procedure is applied to second-order differential delay equations associated with synchronization in electro-optical devices. In all cases, the departure with respect to perfect synchronization is measured through a similarity function. Numerical simulations in discrete maps associated with the hyperchaotic dynamics support the formalism.

Generalized dislocated lag function projective synchronization of fractional order chaotic systems with fully uncertain parameters

International Nuclear Information System (INIS)

Wang, Cong; Zhang, Hong-li; Fan, Wen-hui

2017-01-01

In this paper, we propose a new method to improve the safety of secure communication. This method uses the generalized dislocated lag projective synchronization and function projective synchronization to form a new generalized dislocated lag function projective synchronization. Moreover, this paper takes the examples of fractional order Chen system and Lü system with uncertain parameters as illustration. As the parameters of the two systems are uncertain, the nonlinear controller and parameter update algorithms are designed based on the fractional stability theory and adaptive control method. Moreover, this synchronization form and method of control are applied to secure communication via chaotic masking modulation. Many information signals can be recovered and validated. Finally, simulations are used to show the validity and feasibility of the proposed scheme.

INTERCULTURAL COMMUNICATION PATTERNS AND LANGUAGE USE IN COMPUTER MEDIATED-COMMUNICATION

OpenAIRE

Adriana Teodorescu

2012-01-01

This paper aims at analyzing the degree to which intercultural communication patterns are embedded in computer-mediated communication. Drawing on Hall's and Hofstede's intercultural communication dimensions, this study evaluates empirically high-versus-low context cultural orientations as reflected in the electronic medium, namely the blog, in three different cultures. Cultural variation is also analyzed in linguistic features and communication style in a synchronous mode of communication, by...

Parameter study of global and cluster synchronization in arrays of dry friction oscillators

Energy Technology Data Exchange (ETDEWEB)

Marszal, Michał, E-mail: michal.marszal@p.lodz.pl; Stefański, Andrzej

2017-04-18

Highlights: • Synchronization properties in arrays of coupled dry friction oscillators are investigated. • Master stability function in form of two-oscillator probe is used for predicting synchronization thresholds. • Two network topologies are checked: open and closed nearest neighbor coupling. • Regions of complete and cluster synchronization are found in parameter space. - Abstract: We investigate synchronization thresholds in arrays of identical classic stick-slip dry friction oscillators connected in a nearest neighbor fashion in closed and open ring network. Friction force is modeled by smoothened Stribeck model. Arrays of different length are checked in two parameter space (i.e., coupling coefficient vs. excitation frequency) for complete synchronization as well as cluster synchronization. Synchronization thresholds obtained by brute force numerical integration are compared with possible synchronization regions using the concept called master stability function in the form of two-oscillator reference probe. The results show existence of both complete synchronization and cluster synchronization regions in the investigated systems and confirm that two-oscillator probe can be applied for prediction of synchronization thresholds in systems with stick-slip phenomenon.

An Inter-Networking Mechanism with Stepwise Synchronization for Wireless Sensor Networks

Directory of Open Access Journals (Sweden)

Masayuki Murata

2011-08-01

Full Text Available To realize the ambient information society, multiple wireless networks deployed in the region and devices carried by users are required to cooperate with each other. Since duty cycles and operational frequencies are different among networks, we need a mechanism to allow networks to efficiently exchange messages. For this purpose, we propose a novel inter-networking mechanism where two networks are synchronized with each other in a moderate manner, which we call stepwise synchronization. With our proposal, to bridge the gap between intrinsic operational frequencies, nodes near the border of networks adjust their operational frequencies in a stepwise fashion based on the pulse-coupled oscillator model as a fundamental theory of synchronization. Through simulation experiments, we show that the communication delay and the energy consumption of border nodes are reduced, which enables wireless sensor networks to communicate longer with each other.

Synchronization of generalized Henon map via backstepping design

International Nuclear Information System (INIS)

Huang Lilian; Wang Mao; Feng Rupeng

2005-01-01

This paper proposes a backstepping method to resolve the synchronization of discrete-time chaotic systems. The proposed scheme offers systematic design method for the synchronization of a class of discrete-time hyper-chaotic systems, which implies much complicated high-order chaotic systems can be used to improve the security in chaos communications. A well-known chaotic systems: generalized Henon map is considered as illustrative example to demonstrate the general applicability of backstepping design. Numerical simulations verify the effectiveness of the approach

Time signal distribution in communication networks based on synchronous digital hierarchy

Science.gov (United States)

Imaoka, Atsushi; Kihara, Masami

1993-01-01

A new method that uses round-trip paths to accurately measure transmission delay for time synchronization is proposed. The performance of the method in Synchronous Digital Hierarchy networks is discussed. The feature of this method is that it separately measures the initial round trip path delay and the variations in round-trip path delay. The delay generated in SDH equipment is determined by measuring the initial round-trip path delay. In an experiment with actual SDH equipment, the error of initial delay measurement was suppressed to 30ns.

Designing Learning Resources in Synchronous Learning Environments

DEFF Research Database (Denmark)

Christiansen, Rene B

2015-01-01

Computer-mediated Communication (CMC) and synchronous learning environments offer new solutions for teachers and students that transcend the singular one-way transmission of content knowledge from teacher to student. CMC makes it possible not only to teach computer mediated but also to design...... and create new learning resources targeted to a specific group of learners. This paper addresses the possibilities of designing learning resources within synchronous learning environments. The empirical basis is a cross-country study involving students and teachers in primary schools in three Nordic...... Countries (Denmark, Sweden and Norway). On the basis of these empirical studies a set of design examples is drawn with the purpose of showing how the design fulfills the dual purpose of functioning as a remote, synchronous learning environment and - using the learning materials used and recordings...

Adaptive control and synchronization of a fractional-order chaotic ...

Indian Academy of Sciences (India)

Fractional order; adaptive scheme; control; synchronization. ... College of Physics and Electronics, Hunan Institute of Science and Technology, ... of Information and Communication Engineering, Hunan Institute of Science and Technology, ...

System Design for Nano-Network Communications

Science.gov (United States)

ShahMohammadian, Hoda

The potential applications of nanotechnology in a wide range of areas necessities nano-networking research. Nano-networking is a new type of networking which has emerged by applying nanotechnology to communication theory. Therefore, this dissertation presents a framework for physical layer communications in a nano-network and addresses some of the pressing unsolved challenges in designing a molecular communication system. The contribution of this dissertation is proposing well-justified models for signal propagation, noise sources, optimum receiver design and synchronization in molecular communication channels. The design of any communication system is primarily based on the signal propagation channel and noise models. Using the Brownian motion and advection molecular statistics, separate signal propagation and noise models are presented for diffusion-based and flow-based molecular communication channels. It is shown that the corrupting noise of molecular channels is uncorrelated and non-stationary with a signal dependent magnitude. The next key component of any communication system is the reception and detection process. This dissertation provides a detailed analysis of the effect of the ligand-receptor binding mechanism on the received signal, and develops the first optimal receiver design for molecular communications. The bit error rate performance of the proposed receiver is evaluated and the impact of medium motion on the receiver performance is investigated. Another important feature of any communication system is synchronization. In this dissertation, the first blind synchronization algorithm is presented for the molecular communication channels. The proposed algorithm uses a non-decision directed maximum likelihood criterion for estimating the channel delay. The Cramer-Rao lower bound is also derived and the performance of the proposed synchronization algorithm is evaluated by investigating its mean square error.

A Novel Method of Clock Synchronization in Distributed Systems

Science.gov (United States)

Li, Gun; Niu, Meng-jie; Chai, Yang-shun; Chen, Xin; Ren, Yan-qiu

2017-04-01

Time synchronization plays an important role in the spacecraft formation flight and constellation autonomous navigation, etc. For the application of clock synchronization in a network system, it is not always true that all the observed nodes in the network are interconnected, therefore, it is difficult to achieve the high-precision time synchronization of a network system in the condition that a certain node can only obtain the measurement information of clock from a single neighboring node, but cannot obtain it from other nodes. Aiming at this problem, a novel method of high-precision time synchronization in a network system is proposed. In this paper, each clock is regarded as a node in the network system, and based on the definition of different topological structures of a distributed system, the three control algorithms of time synchronization under the following three cases are designed: without a master clock (reference clock), with a master clock (reference clock), and with a fixed communication delay in the network system. And the validity of the designed clock synchronization protocol is proved by both stability analysis and numerical simulation.

To Communicate or Not to Communicate: Factors Predicting Passengers' Intentions to Ask a Driver to Stop Text Messaging While Driving.

Science.gov (United States)

Wang, Xiao

2016-01-01

Interpersonal communication is important in health campaigns. This research examined factors that are associated with passengers' intentions to communicate no texting with a texting driver in a scenario where the driver is their friend. Based on survey data collected from 546 college students, results showed that students' attitudes toward communication about no texting while driving were predicted by their utilitarian (i.e., safety), value-expressive, and ego-defensive motivations, in addition to being predicted by self-efficacy and norms. Additional results revealed that empathic concern was correlated with the value-expressive motivation and anticipated guilt. Anticipated guilt, together with attitudes, norms, and efficacy, predicted communication intentions. Results revealed that including attitude functions (motivations) in the reasoned action model could help propose and test theory-based predictions in interpersonal communication and health behaviors.

Projective synchronization of time-varying delayed neural network with adaptive scaling factors

International Nuclear Information System (INIS)

Ghosh, Dibakar; Banerjee, Santo

2013-01-01

Highlights: • Projective synchronization in coupled delayed neural chaotic systems with modulated delay time is introduced. • An adaptive rule for the scaling factors is introduced. • This scheme is highly applicable in secure communication. -- Abstract: In this work, the projective synchronization between two continuous time delayed neural systems with time varying delay is investigated. A sufficient condition for synchronization for the coupled systems with modulated delay is presented analytically with the help of the Krasovskii–Lyapunov approach. The effect of adaptive scaling factors on synchronization are also studied in details. Numerical simulations verify the effectiveness of the analytic results

Quantized Synchronization of Chaotic Neural Networks With Scheduled Output Feedback Control.

Science.gov (United States)

Wan, Ying; Cao, Jinde; Wen, Guanghui

In this paper, the synchronization problem of master-slave chaotic neural networks with remote sensors, quantization process, and communication time delays is investigated. The information communication channel between the master chaotic neural network and slave chaotic neural network consists of several remote sensors, with each sensor able to access only partial knowledge of output information of the master neural network. At each sampling instants, each sensor updates its own measurement and only one sensor is scheduled to transmit its latest information to the controller's side in order to update the control inputs for the slave neural network. Thus, such communication process and control strategy are much more energy-saving comparing with the traditional point-to-point scheme. Sufficient conditions for output feedback control gain matrix, allowable length of sampling intervals, and upper bound of network-induced delays are derived to ensure the quantized synchronization of master-slave chaotic neural networks. Lastly, Chua's circuit system and 4-D Hopfield neural network are simulated to validate the effectiveness of the main results.In this paper, the synchronization problem of master-slave chaotic neural networks with remote sensors, quantization process, and communication time delays is investigated. The information communication channel between the master chaotic neural network and slave chaotic neural network consists of several remote sensors, with each sensor able to access only partial knowledge of output information of the master neural network. At each sampling instants, each sensor updates its own measurement and only one sensor is scheduled to transmit its latest information to the controller's side in order to update the control inputs for the slave neural network. Thus, such communication process and control strategy are much more energy-saving comparing with the traditional point-to-point scheme. Sufficient conditions for output feedback control

Synthesis for robust synchronization of chaotic systems under output feedback control with multiple random delays

International Nuclear Information System (INIS)

Wen Guilin; Wang Qingguo; Lin Chong; Han Xu; Li Guangyao

2006-01-01

Synchronization under output feedback control with multiple random time delays is studied, using the paradigm in nonlinear physics-Chua's circuit. Compared with other synchronization control methods, output feedback control with multiple random delay is superior for a realistic synchronization application to secure communications. Sufficient condition for global stability of delay-dependent synchronization is established based on the LMI technique. Numerical simulations fully support the analytical approach, in spite of the random delays

A Methodology for the Design and Verification of Globally Asynchronous/Locally Synchronous Architectures

Science.gov (United States)

Miller, Steven P.; Whalen, Mike W.; O'Brien, Dan; Heimdahl, Mats P.; Joshi, Anjali

2005-01-01

Recent advanced in model-checking have made it practical to formally verify the correctness of many complex synchronous systems (i.e., systems driven by a single clock). However, many computer systems are implemented by asynchronously composing several synchronous components, where each component has its own clock and these clocks are not synchronized. Formal verification of such Globally Asynchronous/Locally Synchronous (GA/LS) architectures is a much more difficult task. In this report, we describe a methodology for developing and reasoning about such systems. This approach allows a developer to start from an ideal system specification and refine it along two axes. Along one axis, the system can be refined one component at a time towards an implementation. Along the other axis, the behavior of the system can be relaxed to produce a more cost effective but still acceptable solution. We illustrate this process by applying it to the synchronization logic of a Dual Fight Guidance System, evolving the system from an ideal case in which the components do not fail and communicate synchronously to one in which the components can fail and communicate asynchronously. For each step, we show how the system requirements have to change if the system is to be implemented and prove that each implementation meets the revised system requirements through modelchecking.

Adaptive synchronization of uncertain chaotic colpitts oscillators based on parameter identification

International Nuclear Information System (INIS)

Fotsin, H.B.; Daafouz, J.

2005-01-01

This Letter uses systematic tools from recent papers to design non-linear observers for synchronization of a chaotic colpitts oscillator both in the non adaptive and adaptive cases. It is shown that all parameters of a totally uncertain model of the oscillator can be estimated through adaptive synchronization. A strategy for practical implementation of a secure communication strategy is also discussed

Positive predictive value of additional synchronous breast lesions in whole-breast ultrasonography at the diagnosis of breast cancer: clinical and imaging factors

International Nuclear Information System (INIS)

Kim, Ah Hyun; Kim, Min Jung; Kim, Eun Kyung; Moon, Hee Jung; Park, Hee Jung

2014-01-01

To evaluate the positive predictive value (PPV) of bilateral whole-breast ultrasonography (BWBU) for detection of synchronous breast lesions on initial diagnosis of breast cancer and evaluate factors affecting the PPV of BWBU according to varying clinicoimaging factors. A total of 75 patients who had synchronous lesions with pathologic confirmation at the initial diagnosis of breast cancer during January 2007 and December 2007 were included. The clinical factors of the patients were evaluated. One observer retrospectively reviewed the imaging studies of the index breast cancer lesion and the synchronous lesion. The PPV for additional biopsy was calculated for BWBU and various clinical and imaging factors affecting the PPV for BWBU were evaluated. The overall PPV for additional biopsy was 25.7% (18 of 70). The PPV for synchronous lesions detected both on mammography and BWBU, and detected only on BWBU, was 76.9% (10 of 13) and 14.3% (7 of 49), respectively. There was no clinical factor affecting the PPV for BWBU. Among the imaging factors, ipsilateral location of the synchronous lesion to the index lesion (P=0.06) showed a marginal statistically significant correlation with malignancy in the synchronous breast lesion. A mass with calcification on mammography presentation (P<0.01), presence of calcification among the ultrasonography findings (P<0.01), and high Breast Imaging Reporting and Data System final assessment (P<0.01) were imaging factors that were associated with malignancy in the additional synchronous lesion. BWBU can detect additional synchronous malignancy at the diagnosis of breast cancer with a relatively high PPV, especially when mammography findings are correlated with ultrasonographic findings.

Learning and Teaching in a Synchronous Collaborative Environment.

Science.gov (United States)

Marjanovic, Olivera

1999-01-01

Describes a new synchronous collaborative environment that combines interactive learning and Group Support Systems for computer-mediated collaboration. Illustrates its potential to improve critical thinking, problem solving, and communication skills, and describes how teachers' roles are changed. (Author/LRW)

Synchronization of three electrochemical oscillators: From local to global coupling

Science.gov (United States)

Liu, Yifan; Sebek, Michael; Mori, Fumito; Kiss, István Z.

2018-04-01

We investigate the formation of synchronization patterns in an oscillatory nickel electrodissolution system in a network obtained by superimposing local and global coupling with three electrodes. We explored the behavior through numerical simulations using kinetic ordinary differential equations, Kuramoto type phase models, and experiments, in which the local to global coupling could be tuned by cross resistances between the three nickel wires. At intermediate coupling strength with predominant global coupling, two of the three oscillators, whose natural frequencies are closer, can synchronize. By adding even a relatively small amount of local coupling (about 9%-25%), a spatially organized partially synchronized state can occur where one of the two synchronized elements is in the center. A formula was derived for predicting the critical coupling strength at which full synchronization will occur independent of the permutation of the natural frequencies of the oscillators over the network. The formula correctly predicts the variation of the critical coupling strength as a function of the global coupling fraction, e.g., with local coupling the critical coupling strength is about twice than that required with global coupling. The results show the importance of the topology of the network on the synchronization properties in a simple three-oscillator setup and could provide guidelines for decrypting coupling topology from identification of synchronization patterns.

Small-world networks exhibit pronounced intermittent synchronization

Science.gov (United States)

Choudhary, Anshul; Mitra, Chiranjit; Kohar, Vivek; Sinha, Sudeshna; Kurths, Jürgen

2017-11-01

We report the phenomenon of temporally intermittently synchronized and desynchronized dynamics in Watts-Strogatz networks of chaotic Rössler oscillators. We consider topologies for which the master stability function (MSF) predicts stable synchronized behaviour, as the rewiring probability (p) is tuned from 0 to 1. MSF essentially utilizes the largest non-zero Lyapunov exponent transversal to the synchronization manifold in making stability considerations, thereby ignoring the other Lyapunov exponents. However, for an N-node networked dynamical system, we observe that the difference in its Lyapunov spectra (corresponding to the N - 1 directions transversal to the synchronization manifold) is crucial and serves as an indicator of the presence of intermittently synchronized behaviour. In addition to the linear stability-based (MSF) analysis, we further provide global stability estimate in terms of the fraction of state-space volume shared by the intermittently synchronized state, as p is varied from 0 to 1. This fraction becomes appreciably large in the small-world regime, which is surprising, since this limit has been otherwise considered optimal for synchronized dynamics. Finally, we characterize the nature of the observed intermittency and its dominance in state-space as network rewiring probability (p) is varied.

Novel communication scheme based on chaotic Roessler circuits

International Nuclear Information System (INIS)

GarcIa-Lopez, J H; Jaimes-Reategui, R; Pisarchik, A N; MurguIa-Hernandez, A; Medina-Gutierrez, C; Valdivia-Hernadez, R; Villafana-Rauda, E

2005-01-01

We present a novel synchronization scheme for secure communication with two chaotic unidirectionally coupled Roessler circuits. The circuits are synchronized via one of the variables, while a signal is transmitted through another variable. We show that this scheme allows more stable communications. The system dynamics is studied numerically and experimentally in a wide range of a control parameter. The possibility of secure communications with an audio signal is demonstrated

Stability analysis and synchronization in discrete-time complex networks with delayed coupling

Science.gov (United States)

Cheng, Ranran; Peng, Mingshu; Yu, Weibin; Sun, Bo; Yu, Jinchen

2013-12-01

A new network of coupled maps is proposed in which the connections between units involve no delays but the intra-neural communication does, whereas in the work of Atay et al. [Phys. Rev. Lett. 92, 144101 (2004)], the focus is on information processing delayed by the inter-neural communication. We show that the synchronization of the network depends on not only the intrinsic dynamical features and inter-connection topology (characterized by the spectrum of the graph Laplacian) but also the delays and the coupling strength. There are two main findings: (i) the more neighbours, the easier to be synchronized; (ii) odd delays are easier to be synchronized than even ones. In addition, compared with those discussed by Atay et al. [Phys. Rev. Lett. 92, 144101 (2004)], our model has a better synchronizability for regular networks and small-world variants.

Adaptive Synchronization of Memristor-based Chaotic Neural Systems

Directory of Open Access Journals (Sweden)

Xiaofang Hu

2014-11-01

Full Text Available Chaotic neural networks consisting of a great number of chaotic neurons are able to reproduce the rich dynamics observed in biological nervous systems. In recent years, the memristor has attracted much interest in the efficient implementation of artificial synapses and neurons. This work addresses adaptive synchronization of a class of memristor-based neural chaotic systems using a novel adaptive backstepping approach. A systematic design procedure is presented. Simulation results have demonstrated the effectiveness of the proposed adaptive synchronization method and its potential in practical application of memristive chaotic oscillators in secure communication.

Synchronicity, Quantum Information and the Psyche

CERN Document Server

Martin, Francois; Galli Carminati, Giuliana

2009-01-01

In this paper we describe synchronicity phenomena. As an explanation of these phenomena we propose quantum entanglement between the psychic realm known as the "unconscious" and also the classical illusion of the collapse of the wave-function. Then, taking the theory of quantum information as a model we consider the human unconscious, pre-consciousness and consciousness as sets of quantum bits (qu-bits). We analyze how there can be communication between these various qu-bit sets. In doing this we are inspired by the theory of nuclear magnetic resonance. In this manner we build quantum processes that permit consciousness to "read" the unconscious and vice-versa. The most elementary interaction, e.g. between a pre-consciousness qu-bit and a consciousness one, allows us to predict the time evolution of the pre-consciousness + consciousness system in which pre-consciousness and consciousness are quantum entangled. This time evolution exhibits Rabi oscillations that we name mental Rabi oscillations. This time evolu...

Synchronized movement experience enhances peer cooperation in preschool children.

Science.gov (United States)

Rabinowitch, Tal-Chen; Meltzoff, Andrew N

2017-08-01

Cooperating with other people is a key achievement in child development and is essential for human culture. We examined whether we could induce 4-year-old children to increase their cooperation with an unfamiliar peer by providing the peers with synchronized motion experience prior to the tasks. Children were randomly assigned to independent treatment and control groups. The treatment of synchronous motion caused children to enhance their cooperation, as measured by the speed of joint task completion, compared with control groups that underwent asynchronous motion or no motion at all. Further analysis suggested that synchronization experience increased intentional communication between peer partners, resulting in increased coordination and cooperation. Copyright © 2017 Elsevier Inc. All rights reserved.

Experimental study of chaos synchronization in the Belousov-Zhabotinsky chemical system

International Nuclear Information System (INIS)

Li Yanni; Chen Lan; Cai Zunsheng; Zhao Xuezhuang

2004-01-01

Employing self-adaptive parameter regulation scheme, chaos synchronization in the Belousov-Zhabotinsky-CSTR chemical system has been studied experimentally. By optimizing the combination of regulation parameters, the trend of chaos synchronization is observed and the prediction of chaos synchronization from numerical simulation is thus verified by the experiment. In addition, the difference of sensitivity to noise with the mass coupling scheme and the self-adaptive parameter regulation scheme in chaos synchronization has also been discussed

Synchronous Modeling of Modular Avionics Architectures using the SIGNAL Language

OpenAIRE

Gamatié , Abdoulaye; Gautier , Thierry

2002-01-01

This document presents a study on the modeling of architecture components for avionics applications. We consider the avionics standard ARINC 653 specifications as basis, as well as the synchronous language SIGNAL to describe the modeling. A library of APEX object models (partition, process, communication and synchronization services, etc.) has been implemented. This should allow to describe distributed real-time applications using POLYCHRONY, so as to access formal tools and techniques for ar...

Switched generalized function projective synchronization of two identical/different hyperchaotic systems with uncertain parameters

International Nuclear Information System (INIS)

Li Hongmin; Li Chunlai

2012-01-01

In this paper, we investigate two switched synchronization schemes, namely partial and complete switched generalized function projective synchronization, by using the adaptive control method. Partial switched synchronization of chaotic systems means that the state variables of the drive system synchronize with partial different state variables of the response system, whereas complete switched synchronization of chaotic systems means that all the state variables of the drive system synchronize with complete different state variables of the response system. Because the switched synchronization scheme exists in many combinations, it is a promising type of synchronization as it provides greater security in secure communications. Based on the Lyapunov stability theory, the adaptive control laws and the parameter update laws are derived to make the states of two identical/different hyperchaotic systems asymptotically synchronized up to a desired scaling function. Finally, numerical simulations are performed to verify and illustrate the analytical results.

Extension of Pairwise Broadcast Clock Synchronization for Multicluster Sensor Networks

Directory of Open Access Journals (Sweden)

Bruce W. Suter

2008-01-01

Full Text Available Time synchronization is crucial for wireless sensor networks (WSNs in performing a number of fundamental operations such as data coordination, power management, security, and localization. The Pairwise Broadcast Synchronization (PBS protocol was recently proposed to minimize the number of timing messages required for global network synchronization, which enables the design of highly energy-efficient WSNs. However, PBS requires all nodes in the network to lie within the communication ranges of two leader nodes, a condition which might not be available in some applications. This paper proposes an extension of PBS to the more general class of sensor networks. Based on the hierarchical structure of the network, an energy-efficient pair selection algorithm is proposed to select the best pairwise synchronization sequence to reduce the overall energy consumption. It is shown that in a multicluster networking environment, PBS requires a far less number of timing messages than other well-known synchronization protocols and incurs no loss in synchronization accuracy. Moreover, the proposed scheme presents significant energy savings for densely deployed WSNs.

Shape synchronization control for three-dimensional chaotic systems

International Nuclear Information System (INIS)

Huang, Yuanyuan; Wang, Yinhe; Chen, Haoguang; Zhang, Siying

2016-01-01

This paper aims to the three-dimensional continuous chaotic system and shape of the chaotic attractor by utilizing the basic theory of plane curves in classical differential geometry, the continuous controller is synthesized for the master–slave synchronization in shape. This means that the slave system can possess the same shape of state trajectory with the master system via the continuous controller. The continuous controller is composed of three sub-controllers, which respectively correspond to the master–slave synchronization in shape for the three projective curves of the chaotic attractor onto the three coordinate planes. Moreover, the proposed shape synchronization technique as well as application of control scheme to secure communication is also demonstrated in this paper, where numerical simulation results show the proposed control method works well.

Predictive control of a chaotic permanent magnet synchronous generator in a wind turbine system

Science.gov (United States)

Manal, Messadi; Adel, Mellit; Karim, Kemih; Malek, Ghanes

2015-01-01

This paper investigates how to address the chaos problem in a permanent magnet synchronous generator (PMSG) in a wind turbine system. Predictive control approach is proposed to suppress chaotic behavior and make operating stable; the advantage of this method is that it can only be applied to one state of the wind turbine system. The use of the genetic algorithms to estimate the optimal parameter values of the wind turbine leads to maximization of the power generation. Moreover, some simulation results are included to visualize the effectiveness and robustness of the proposed method. Project supported by the CMEP-TASSILI Project (Grant No. 14MDU920).

Frequency-domain criterion for the chaos synchronization of time ...

Indian Academy of Sciences (India)

of time-delay power systems under linear feedback control ... arbitrary dimension of the time-delay systems can keep their chaotic characteristic as long as ... As a basic theory on chaotic secure communication, synchronization of time-delay.

Robust and Low-Complexity Timing Synchronization Algorithm and its Architecture for ADSRC Applications

Directory of Open Access Journals (Sweden)

KIM, J.

2009-10-01

Full Text Available 5.9 GHz advanced dedicated short range communications (ADSRC is a short-to-medium range communication standard that supports both public safety and private operations in roadside-to-vehicle and vehicle-to-vehicle communication environments. The core technology of physical layer in ADSRC is orthogonal frequency division multiplexing (OFDM, which is sensitive to timing synchronization error. In this paper, a robust and low-complexity timing synchronization algorithm suitable for ADSRC system and its efficient hardware architecture are proposed. The implementation of the proposed architecture is performed with Xilinx Vertex-II XC2V1000 Field Programmable Gate Array (FPGA. The proposed algorithm is based on cross-correlation technique, which is employed to detect the starting point of short training symbol and the guard interval of the long training symbol. Synchronization error rate (SER evaluation results and post-layout simulation results show that the proposed algorithm is efficient in high-mobility environments. The post-layout results of implementation demonstrate the robustness and low-complexity of the proposed architecture.

Generalized synchronization and coherent structures in spatially extended systems

International Nuclear Information System (INIS)

Basnarkov, Lasko; Duane, Gregory S.; Kocarev, Ljupco

2014-01-01

We study the synchronization of a coupled pair of one-dimensional Kuramoto–Sivashinsky systems, with equations augmented by a third-space-derivative term. With two different values of a system parameter, the two systems synchronize in the generalized sense. The phenomenon persists even in the extreme case when one of the equations is missing the extra term. Master–slave synchronization error is small, so the generalized synchronization relationship is useful for predicting the state of the master from that of the slave, or conversely, for controlling the slave. The spatial density of coupling points required to bring about generalized synchronization appears to be related to the wavelength of traveling wave solutions, and more generally to the width of coherent structures in the separate systems

Emergence of a super-synchronized mobbing state in a large population of coupled chemical oscillators

Science.gov (United States)

Ghoshal, Gourab; Muñuzuri, Alberto P.; Pérez-Mercader, Juan

2016-01-01

Oscillatory phenomena are ubiquitous in Nature. The ability of a large population of coupled oscillators to synchronize constitutes an important mechanism to express information and establish communication among members. To understand such phenomena, models and experimental realizations of globally coupled oscillators have proven to be invaluable in settings as varied as chemical, biological and physical systems. A variety of rich dynamical behavior has been uncovered, although usually in the context of a single state of synchronization or lack thereof. Through the experimental and numerical study of a large population of discrete chemical oscillators, here we report on the unexpected discovery of a new phenomenon revealing the existence of dynamically distinct synchronized states reflecting different degrees of communication. Specifically, we discover a novel large-amplitude super-synchronized state separated from the conventionally reported synchronized and quiescent states through an unusual sharp jump transition when sampling the strong coupling limit. Our results assume significance for further elucidating globally coherent phenomena, such as in neuropathologies, bacterial cell colonies, social systems and semiconductor lasers.

The Functional Role of Neural Oscillations in Non-Verbal Emotional Communication.

Science.gov (United States)

Symons, Ashley E; El-Deredy, Wael; Schwartze, Michael; Kotz, Sonja A

2016-01-01

Effective interpersonal communication depends on the ability to perceive and interpret nonverbal emotional expressions from multiple sensory modalities. Current theoretical models propose that visual and auditory emotion perception involves a network of brain regions including the primary sensory cortices, the superior temporal sulcus (STS), and orbitofrontal cortex (OFC). However, relatively little is known about how the dynamic interplay between these regions gives rise to the perception of emotions. In recent years, there has been increasing recognition of the importance of neural oscillations in mediating neural communication within and between functional neural networks. Here we review studies investigating changes in oscillatory activity during the perception of visual, auditory, and audiovisual emotional expressions, and aim to characterize the functional role of neural oscillations in nonverbal emotion perception. Findings from the reviewed literature suggest that theta band oscillations most consistently differentiate between emotional and neutral expressions. While early theta synchronization appears to reflect the initial encoding of emotionally salient sensory information, later fronto-central theta synchronization may reflect the further integration of sensory information with internal representations. Additionally, gamma synchronization reflects facilitated sensory binding of emotional expressions within regions such as the OFC, STS, and, potentially, the amygdala. However, the evidence is more ambiguous when it comes to the role of oscillations within the alpha and beta frequencies, which vary as a function of modality (or modalities), presence or absence of predictive information, and attentional or task demands. Thus, the synchronization of neural oscillations within specific frequency bands mediates the rapid detection, integration, and evaluation of emotional expressions. Moreover, the functional coupling of oscillatory activity across multiples

INTERCULTURAL COMMUNICATION PATTERNS AND LANGUAGE USE IN COMPUTER MEDIATED-COMMUNICATION

Directory of Open Access Journals (Sweden)

Adriana Teodorescu

2012-11-01

Full Text Available This paper aims at analyzing the degree to which intercultural communication patterns are embedded in computer-mediated communication. Drawing on Hall’s and Hofstede’s intercultural communication dimensions, this study evaluates empirically high-versus-low context cultural orientations as reflected in the electronic medium, namely the blog, in three different cultures. Cultural variation is also analyzed in linguistic features and communication style in a synchronous mode of communication, by investigating data from several popular blogs from Japan, Germany and Italy.

Event-related theta synchronization predicts deficit in facial affect recognition in schizophrenia.

Science.gov (United States)

Csukly, Gábor; Stefanics, Gábor; Komlósi, Sarolta; Czigler, István; Czobor, Pál

2014-02-01

Growing evidence suggests that abnormalities in the synchronized oscillatory activity of neurons in schizophrenia may lead to impaired neural activation and temporal coding and thus lead to neurocognitive dysfunctions, such as deficits in facial affect recognition. To gain an insight into the neurobiological processes linked to facial affect recognition, we investigated both induced and evoked oscillatory activity by calculating the Event Related Spectral Perturbation (ERSP) and the Inter Trial Coherence (ITC) during facial affect recognition. Fearful and neutral faces as well as nonface patches were presented to 24 patients with schizophrenia and 24 matched healthy controls while EEG was recorded. The participants' task was to recognize facial expressions. Because previous findings with healthy controls showed that facial feature decoding was associated primarily with oscillatory activity in the theta band, we analyzed ERSP and ITC in this frequency band in the time interval of 140-200 ms, which corresponds to the N170 component. Event-related theta activity and phase-locking to facial expressions, but not to nonface patches, predicted emotion recognition performance in both controls and patients. Event-related changes in theta amplitude and phase-locking were found to be significantly weaker in patients compared with healthy controls, which is in line with previous investigations showing decreased neural synchronization in the low frequency bands in patients with schizophrenia. Neural synchrony is thought to underlie distributed information processing. Our results indicate a less effective functioning in the recognition process of facial features, which may contribute to a less effective social cognition in schizophrenia. PsycINFO Database Record (c) 2014 APA, all rights reserved.

A Review Of Estrus Synchronization Technology In Cattle | Anyam ...

African Journals Online (AJOL)

Manipulation of the oestrous cycle by the use of synchronizing agents to enhance the function of the reproductive organs has proved beneficial to livestock production. Estrus synchronization has enabled a large number of cows to be bred at the same time with subsequent calving at a predictable time. Various estrous cycle ...

Firefly Clock Synchronization in an 802.15.4 Wireless Network

Directory of Open Access Journals (Sweden)

Elmenreich Wilfried

2009-01-01

Full Text Available This paper describes the design and implementation of a distributed self-stabilizing clock synchronization algorithm based on the biological example of Asian Fireflies. Huge swarms of these fireflies use the principle of pulse coupled oscillators in order to synchronously emit light flashes to attract mating partners. When applying this algorithm to real sensor networks, typically, nodes cannot receive messages while transmitting, which prevents the networked nodes from reaching synchronization. In order to counteract this deafness problem, we adopt a variant of the Reachback Firefly Algorithm to distribute the timing of light flashes in a given time window without affecting the quality of the synchronization. A case study implemented on 802.15.4 Zigbee nodes presents the application of this approach for a time-triggered communication scheduling and coordinated duty cycling in order to enhance the battery lifetime of the nodes.

Synchronization and anti-synchronization coexist in Chen-Lee chaotic systems

International Nuclear Information System (INIS)

Chen, J.-H.; Chen, H.-K.; Lin, Y.-K.

2009-01-01

This study demonstrates that synchronization and anti-synchronization can coexist in Chen-Lee chaotic systems by direct linear coupling. Based on Lyapunov's direct method, a linear controller was designed to assure that two different types of synchronization can simultaneously be achieved. Further, the hybrid projective synchronization of Chen-Lee chaotic systems was studied using a nonlinear control scheme. The nonlinear controller was designed according to the Lyapunov stability theory to guarantee the hybrid projective synchronization, including synchronization, anti-synchronization, and projective synchronization. Finally, numerical examples are presented in order to illustrate the proposed synchronization approach.

Time-Predictable Communication on a Time-Division Multiplexing Network-on-Chip Multicore

DEFF Research Database (Denmark)

Sørensen, Rasmus Bo

This thesis presents time-predictable inter-core communication on a multicore platform with a time-division multiplexing (TDM) network-on-chip (NoC) for hard real-time systems. The thesis is structured as a collection of papers that contribute within the areas of: reconfigurable TDM NoCs, static...... TDM scheduling, and time-predictable inter-core communication. More specifically, the work presented in this thesis investigates the interaction between hardware and software involved in time-predictable inter-core communication on the multicore platform. The thesis presents: a new generation...... of the Argo NoC network interface (NI) that supports instantaneous reconfiguration, a TDM traffic scheduler that generates virtual circuit (VC) configurations for the Argo NoC, and software functions for two types of intercore communication. The new generation of the Argo NoC adds the capability...

On the improvement of neural cryptography using erroneous transmitted information with error prediction.

Science.gov (United States)

Allam, Ahmed M; Abbas, Hazem M

2010-12-01

Neural cryptography deals with the problem of "key exchange" between two neural networks using the mutual learning concept. The two networks exchange their outputs (in bits) and the key between the two communicating parties is eventually represented in the final learned weights, when the two networks are said to be synchronized. Security of neural synchronization is put at risk if an attacker is capable of synchronizing with any of the two parties during the training process. Therefore, diminishing the probability of such a threat improves the reliability of exchanging the output bits through a public channel. The synchronization with feedback algorithm is one of the existing algorithms that enhances the security of neural cryptography. This paper proposes three new algorithms to enhance the mutual learning process. They mainly depend on disrupting the attacker confidence in the exchanged outputs and input patterns during training. The first algorithm is called "Do not Trust My Partner" (DTMP), which relies on one party sending erroneous output bits, with the other party being capable of predicting and correcting this error. The second algorithm is called "Synchronization with Common Secret Feedback" (SCSFB), where inputs are kept partially secret and the attacker has to train its network on input patterns that are different from the training sets used by the communicating parties. The third algorithm is a hybrid technique combining the features of the DTMP and SCSFB. The proposed approaches are shown to outperform the synchronization with feedback algorithm in the time needed for the parties to synchronize.

Inter-Destination Multimedia Synchronization: Schemes, Use Cases and Standardization

NARCIS (Netherlands)

Montagud, M.; Boronat, F.; Stokking, H.M.; Brandenburg, R. van

2012-01-01

Traditionally, the media consumption model has been a passive and isolated activity. However, the advent of media streaming technologies, interactive social applications, and synchronous communications, as well as the convergence between these three developments, point to an evolution towards

Nonlinear observer for synchronization of chaotic systems with application to secure data transmission

Science.gov (United States)

Aguilar-López, Ricardo; Martínez-Guerra, Rafael; Perez-Pinacho, Claudia A.

2014-06-01

The main issue of this work is related with the design of a class of nonlinear observer in order to synchronize chaotic dynamical systems in a master-slave scheme, considering different initial conditions. The oscillator of Chen is proposed as a benchmark model and a bounded-type observer is proposed to reach synchronicity between both two chaotic systems. The proposed observer contains a proportional and sigmoid form of a bounded function of the synchronization error in order to provide asymptotic synchronization with a satisfactory performance. Some numerical simulations were carrying out in order to show the operation of the proposed methodology, with possible applications to secure data communications issues.

A synchronous serial bus for multidimensional array acoustic logging tool

Science.gov (United States)

Men, Baiyong; Ju, Xiaodong; Lu, Junqiang; Qiao, Wenxiao

2016-12-01

In high-temperature and spatial borehole applications, a distributed structure is employed in a multidimensional array acoustic logging tool (MDALT) based on a phased array technique for electronic systems. However, new challenges, such as synchronous multichannel data acquisition, multinode real-time control and bulk data transmission in a limited interval, have emerged. To address these challenges, we developed a synchronous serial bus (SSB) in this study. SSB works in a half-duplex mode via a master-slave architecture. It also consists of a single master, several slaves, a differential clock line and a differential data line. The clock line is simplex, whereas the data line is half-duplex and synchronous to the clock line. A reliable communication between the master and the slaves with real-time adjustment of synchronisation is achieved by rationally designing the frame format and protocol of communication and by introducing a scramble code and a Hamming error-correcting code. The control logic of the master and the slaves is realized in field programmable gate array (FPGA) or complex programmable logic device (CPLD). The clock speed of SSB is 10 MHz, the effective data rate of the bulk data transmission is over 99%, and the synchronous errors amongst the slaves are less than 10 ns. Room-temperature test, high-temperature test (175 °C) and field test demonstrate that the proposed SSB is qualified for MDALT.

Synchronization of identical chaotic systems through external chaotic driving

International Nuclear Information System (INIS)

Patidar, V.; Sud, K.K.

2005-11-01

In recent years, the study of synchronization of identical chaotic systems subjected to a common fluctuating random driving signal has drawn considerable interest. In this communication, we report that it is possible to achieve synchronization between two identical chaotic systems, which are not coupled directly but subjected to an external chaotic signal. The external chaotic signal may be obtained from any chaotic system identical or non-identical to both identical chaotic systems. Results of numerical simulations on well known Roessler and jerk dynamical systems have been presented. (author)

Navigating Turn-Taking and Conversational Repair in an Online Synchronous Course

Science.gov (United States)

Earnshaw, Yvonne

2017-01-01

In face-to-face conversations, speaker transitions (or hand-offs) are typically seamless. In computer-mediated communication settings, speaker hand-offs can be a bit more challenging. This paper presents the results of a study of audio communication problems that occur in an online synchronous course, and how, and by whom, those problems are…

Files synchronization from a large number of insertions and deletions

Science.gov (United States)

Ellappan, Vijayan; Kumari, Savera

2017-11-01

Synchronization between different versions of files is becoming a major issue that most of the applications are facing. To make the applications more efficient a economical algorithm is developed from the previously used algorithm of “File Loading Algorithm”. I am extending this algorithm in three ways: First, dealing with non-binary files, Second backup is generated for uploaded files and lastly each files are synchronized with insertions and deletions. User can reconstruct file from the former file with minimizing the error and also provides interactive communication by eliminating the frequency without any disturbance. The drawback of previous system is overcome by using synchronization, in which multiple copies of each file/record is created and stored in backup database and is efficiently restored in case of any unwanted deletion or loss of data. That is, to introduce a protocol that user B may use to reconstruct file X from file Y with suitably low probability of error. Synchronization algorithms find numerous areas of use, including data storage, file sharing, source code control systems, and cloud applications. For example, cloud storage services such as Drop box synchronize between local copies and cloud backups each time users make changes to local versions. Similarly, synchronization tools are necessary in mobile devices. Specialized synchronization algorithms are used for video and sound editing. Synchronization tools are also capable of performing data duplication.

A digital bandlimited chaos-based communication system

Science.gov (United States)

Fontes, Rodrigo T.; Eisencraft, Marcio

2016-08-01

In recent years, many communication systems that use a function to encode an information in a chaotic signal were proposed. Since every transmission channel is bandlimited in nature, it is required to determine and to control the chaotic signal spectrum. This way, a bandlimited chaos-based communication system (CBCS) was proposed using digital filters and chaotic synchronization. As the filters modify the original chaotic system, it is necessary to study how their insertion affects chaotic synchronization. In this work, we present a digital discrete-time bandlimited CBCS system analysis, considering practical settings encountered in conventional communication systems. The proposed system is based on master-slave chaotic synchronization and the required conditions for its synchronization is obtained analytically for a general K-dimensional chaos generator map. The performance of this system is evaluated in terms of bit error rate. As a way to improve the signal to noise ratio, we also propose to filter the out-of-band noise in the receiver. Numerical simulations show the advantages of using such a scheme.

Design and Implementation of Recursive Model Predictive Control for Permanent Magnet Synchronous Motor Drives

Directory of Open Access Journals (Sweden)

Xuan Wu

2015-01-01

Full Text Available In order to control the permanent-magnet synchronous motor system (PMSM with different disturbances and nonlinearity, an improved current control algorithm for the PMSM systems using recursive model predictive control (RMPC is developed in this paper. As the conventional MPC has to be computed online, its iterative computational procedure needs long computing time. To enhance computational speed, a recursive method based on recursive Levenberg-Marquardt algorithm (RLMA and iterative learning control (ILC is introduced to solve the learning issue in MPC. RMPC is able to significantly decrease the computation cost of traditional MPC in the PMSM system. The effectiveness of the proposed algorithm has been verified by simulation and experimental results.

Impulsive stabilization and impulsive synchronization of discrete-time delayed neural networks.

Science.gov (United States)

Chen, Wu-Hua; Lu, Xiaomei; Zheng, Wei Xing

2015-04-01

This paper investigates the problems of impulsive stabilization and impulsive synchronization of discrete-time delayed neural networks (DDNNs). Two types of DDNNs with stabilizing impulses are studied. By introducing the time-varying Lyapunov functional to capture the dynamical characteristics of discrete-time impulsive delayed neural networks (DIDNNs) and by using a convex combination technique, new exponential stability criteria are derived in terms of linear matrix inequalities. The stability criteria for DIDNNs are independent of the size of time delay but rely on the lengths of impulsive intervals. With the newly obtained stability results, sufficient conditions on the existence of linear-state feedback impulsive controllers are derived. Moreover, a novel impulsive synchronization scheme for two identical DDNNs is proposed. The novel impulsive synchronization scheme allows synchronizing two identical DDNNs with unknown delays. Simulation results are given to validate the effectiveness of the proposed criteria of impulsive stabilization and impulsive synchronization of DDNNs. Finally, an application of the obtained impulsive synchronization result for two identical chaotic DDNNs to a secure communication scheme is presented.

Gap junctions and inhibitory synapses modulate inspiratory motoneuron synchronization.

Science.gov (United States)

Bou-Flores, C; Berger, A J

2001-04-01

Interneuronal electrical coupling via gap junctions and chemical synaptic inhibitory transmission are known to have roles in the generation and synchronization of activity in neuronal networks. Uncertainty exists regarding the roles of these two modes of interneuronal communication in the central respiratory rhythm-generating system. To assess their roles, we performed studies on both the neonatal mouse medullary slice and en bloc brain stem-spinal cord preparations where rhythmic inspiratory motor activity can readily be recorded from both hypoglossal and phrenic nerve roots. The rhythmic inspiratory activity observed had two temporal characteristics: the basic respiratory frequency occurring on a long time scale and the synchronous neuronal discharge within the inspiratory burst occurring on a short time scale. In both preparations, we observed that bath application of gap-junction blockers, including 18 alpha-glycyrrhetinic acid, 18 beta-glycyrrhetinic acid, and carbenoxolone, all caused a reduction in respiratory frequency. In contrast, peak integrated phrenic and hypoglossal inspiratory activity was not significantly changed by gap-junction blockade. On a short-time-scale, gap-junction blockade increased the degree of synchronization within an inspiratory burst observed in both nerves. In contrast, opposite results were observed with blockade of GABA(A) and glycine receptors. We found that respiratory frequency increased with receptor blockade, and simultaneous blockade of both receptors consistently resulted in a reduction in short-time-scale synchronized activity observed in phrenic and hypoglossal inspiratory bursts. These results support the concept that the central respiratory system has two components: a rhythm generator responsible for the production of respiratory cycle timing and an inspiratory pattern generator that is involved in short-time-scale synchronization. In the neonatal rodent, properties of both components can be regulated by interneuronal

Backoff-stage synchronization in three-hop string-topology wireless networks with hidden nodes

Science.gov (United States)

Sanada, Kosuke; Sekiya, Hiroo; Komuro, Nobuyoshi; Sakata, Shiro

In IEEE 802.11 wireless multi-hop networks, each node works individually and their individual operations generate entire network dynamics. It is important to clarify the network dynamics in wireless multi-hop networks for designing and constructing multi-hop communication networks. This paper presents the network-dynamics investigations for three-hop string-topology wireless network in detail. From the investigations, a “backoff-stage synchronization” phenomenon, which is mutuality between hidden nodes, is found. The mechanism of the backoff-stage synchronization is expressed and the sufficient conditions for the synchronization occurrence are given. This phenomenon gives some impacts on the IEEE 802.11 multi-hop-network communications.

Distributed-observer-based cooperative control for synchronization of linear discrete-time multi-agent systems.

Science.gov (United States)

Liang, Hongjing; Zhang, Huaguang; Wang, Zhanshan

2015-11-01

This paper considers output synchronization of discrete-time multi-agent systems with directed communication topologies. The directed communication graph contains a spanning tree and the exosystem as its root. Distributed observer-based consensus protocols are proposed, based on the relative outputs of neighboring agents. A multi-step algorithm is presented to construct the observer-based protocols. In light of the discrete-time algebraic Riccati equation and internal model principle, synchronization problem is completed. At last, numerical simulation is provided to verify the effectiveness of the theoretical results. Copyright © 2015 ISA. Published by Elsevier Ltd. All rights reserved.

Global chaos synchronization of three coupled nonlinear autonomous systems and a novel method of chaos encryption

International Nuclear Information System (INIS)

An Xinlei; Yu Jianning; Chu Yandong; Zhang Jiangang; Zhang Li

2009-01-01

In this paper, we discussed the fixed points and their linear stability of a new nonlinear autonomous system that introduced by J.C. Sprott. Based on Lyapunov stabilization theorem, a global chaos synchronization scheme of three coupled identical systems is investigated. By choosing proper coupling parameters, the states of all the three systems can be synchronized. Then this method was applied to secure communication through chaotic masking, used three coupled identical systems, propose a novel method of chaos encryption, after encrypting in the previous two transmitters, information signal can be recovered exactly at the receiver end. Simulation results show that the method can realize monotonous synchronization. Further more, the information signal can be recovered undistorted when applying this method to secure communication.

Synchronous Videoconferencing in Distance Education for Pre-Licensure Nursing

Science.gov (United States)

Scarbrough, John E.

2015-01-01

Current nursing education practices typically include methodologies for providing access to students located at a distance from the hosting institution. The majority of methodologies make use of asynchronous formatting in which communication occurs without the benefit of simultaneous, synchronous interaction. The increasing worldwide availability…

Role of synchronized oscillatory brain activity for human pain perception.

Science.gov (United States)

Hauck, Michael; Lorenz, Jürgen; Engel, Andreas K

2008-01-01

The understanding of cortical pain processing in humans has significantly improved since the development of modern neuroimaging techniques. Non-invasive electrophysiological approaches such as electro- and magnetoencephalography have proven to be helpful tools for the real-time investigation of neuronal signals and synchronous communication between cortical areas. In particular, time-frequency decomposition of signals recorded with these techniques seems to be a promising approach because different pain-related oscillatory changes can be observed within different frequency bands, which are likely to be linked to specific sensory and motor functions. In this review we discuss the latest evidence on pain-induced time-frequency signals and propose that changes in oscillatory activity reflect an essential communication mechanism in the brain that is modulated during pain processing. The importance of synchronization processes for normal and pathological pain processing, such as chronic pain states, is discussed.

Cluster synchronization modes in an ensemble of coupled chaotic oscillators

DEFF Research Database (Denmark)

Belykh, Vladimir N.; Belykh, Igor V.; Mosekilde, Erik

2001-01-01

Considering systems of diffusively coupled identical chaotic oscillators, an effective method to determine the possible states of cluster synchronization and ensure their stability is presented. The method, which may find applications in communication engineering and other fields of science...

An application for multi-person task synchronization

Science.gov (United States)

Brown, Robert L.; Doyle, Dee

1990-01-01

Computer applications are studied that will enable a group of people to synchronize their actions when following a predefined task sequence. It is assumed that the people involved only have computer workstations available to them for communication. Hence, the approach is to study how the computer can be used to help a group remain synchronized. A series of applications were designed and developed that can be used as vehicles for experimentation. An example of how this technique can be used for a remote coaching capability is explained in a report describing an experiment that simulated a Life Sciences experiment on-board Space Station Freedom, with a ground based principal investigator providing the expertise by coaching the on-orbit mission specialist.

Chaotic map based key agreement with/out clock synchronization

International Nuclear Information System (INIS)

Han, S.; Chang, E.

2009-01-01

In order to address Bergamo et al.'s attack, Xiao et al. proposed a key agreement protocol using chaotic maps. Han then presented three attacks on Xiao et al.'s protocol. To enhance the security of key agreement based on chaotic maps, Chang et al. proposed a new key agreement using passphrase, which works in clock synchronization environment. However, their protocol still has some issues: one is its passphrase is not easy to remember and much longer than password; the second one is it cannot resist guessing attack if the constructed passphrase is easy to remember and also has already existed in some rational dictionaries; the third one is it cannot work without clock synchronization. In this paper, we will present two different key agreement protocols, which can resist guessing attack. The first one works in clock synchronization environment. The second one can work without clock synchronization. They both use authenticated password for secure communications. The protocols are secure against replaying attacks and a shared session key can be established.

Delay or anticipatory synchronization in one-way coupled systems ...

Indian Academy of Sciences (India)

1Department of Physics, Indian Institute of Science Education and Research, Pune 411 ... Synchronization; variable time delay; time delay systems; secure communication. .... scheme can be defined as y(t − τ2) = x(t − τ1) or y(t) = x(t − τ1 + τ2).

A synchronization method for wireless acquisition systems, application to brain computer interfaces.

Science.gov (United States)

Foerster, M; Bonnet, S; van Langhenhove, A; Porcherot, J; Charvet, G

2013-01-01

A synchronization method for wireless acquisition systems has been developed and implemented on a wireless ECoG recording implant and on a wireless EEG recording helmet. The presented algorithm and hardware implementation allow the precise synchronization of several data streams from several sensor nodes for applications where timing is critical like in event-related potential (ERP) studies. The proposed method has been successfully applied to obtain visual evoked potentials and compared with a reference biosignal amplifier. The control over the exact sampling frequency allows reducing synchronization errors that will otherwise accumulate during a recording. The method is scalable to several sensor nodes communicating with a shared base station.

Self-stabilizing Synchronization in Mobile Sensor Networks with Covering

Science.gov (United States)

Beauquier, Joffroy; Burman, Janna

Synchronization is widely considered as an important service in distributed systems which may simplify protocol design. Phase clock is a general synchronization tool that provides a form of a logical time. This paper presents a self-stabilizing (a tolerating state-corrupting transient faults) phase clock algorithm suited to the model of population protocols with covering. This model has been proposed recently for sensor networks with a very large, possibly unknown number of anonymous mobile agents having small memory. Agents interact in pairs in an asynchronous way subject to the constraints expressed in terms of the cover times of agents. The cover time expresses the "frequency" of an agent to communicate with all the others and abstracts agent's communication characteristics (e.g. moving speed/patterns, transmitting/receiving capabilities). We show that a phase clock is impossible in the model with only constant-state agents. Hence, we assume an existence of resource-unlimited agent - the base station.

Synchronization of delay-coupled nonlinear oscillators: an approach based on the stability analysis of synchronized equilibria.

Science.gov (United States)

Michiels, Wim; Nijmeijer, Henk

2009-09-01

We consider the synchronization problem of an arbitrary number of coupled nonlinear oscillators with delays in the interconnections. The network topology is described by a directed graph. Unlike the conventional approach of deriving directly sufficient synchronization conditions, the approach of the paper starts from an exact stability analysis in a (gain, delay) parameter space of a synchronized equilibrium and extracts insights from an analysis of its bifurcations and from the corresponding emerging behavior. Instrumental to this analysis a factorization of the characteristic equation is employed that not only facilitates the analysis and reduces computational cost but also allows to determine the precise role of the individual agents and the topology of the network in the (in)stability mechanisms. The study provides an algorithm to perform a stability and bifurcation analysis of synchronized equilibria. Furthermore, it reveals fundamental limitations to synchronization and it explains under which conditions on the topology of the network and on the characteristics of the coupling the systems are expected to synchronize. In the second part of the paper the results are applied to coupled Lorenz systems. The main results show that for sufficiently large coupling gains, delay-coupled Lorenz systems exhibit a generic behavior that does not depend on the number of systems and the topology of the network, as long as some basic assumptions are satisfied, including the strong connectivity of the graph. Here the linearized stability analysis is strengthened by a nonlinear stability analysis which confirms the predictions based on the linearized stability and bifurcation analysis. This illustrates the usefulness of the exact linearized analysis in a situation where a direct nonlinear stability analysis is not possible or where it yields conservative conditions from which it is hard to get qualitative insights in the synchronization mechanisms and their scaling properties

Network secure communications based on beam halo-chaos

International Nuclear Information System (INIS)

Liu Qiang; Fang Jinqing; Li Yong

2010-01-01

Based on beam halo-chaos synchronization in the beam transport network (line)with small-world effect, using three synchronization methods:the driver-response synchronization, small-world topology coupling synchronization and multi-local small-world topology coupling synchronization, three kinds of secure communication projects were designed respectively, and were studied numerically by the Simulink tool of the Matlab software. Numerical experimental results demonstrate that encryption and decryption of the original signal are realized successfully. It provides effective theoretical foundation and reference for the next engineering design and network experiment. (authors)

Simulating climate with a synchronization-based supermodel

Science.gov (United States)

Selten, Frank M.; Schevenhoven, Francine J.; Duane, Gregory S.

2017-12-01

The SPEEDO global climate model (an atmosphere model coupled to a land and an ocean/sea-ice model with about 250.000 degrees of freedom) is used to investigate the merits of a new multi-model ensemble approach to the climate prediction problem in a perfect model setting. Two imperfect models are generated by perturbing parameters. Connection terms are introduced that synchronize the two models on a common solution, referred to as the supermodel solution. A synchronization-based learning algorithm is applied to the supermodel through the introduction of an update rule for the connection coefficients. Connection coefficients cease updating when synchronization errors between the supermodel and solutions of the "true" equations vanish. These final connection coefficients define the supermodel. Different supermodel solutions, but with equivalent performance, are found depending on the initial values of the connection coefficients during learning. The supermodels have a climatology and a climate response to a CO2 increase in the atmosphere that is closer to the truth as compared to the imperfect models and the standard multi-model ensemble average, showing the potential of the supermodel approach to improve climate predictions.

Measurement of stress in vocal folds during phonation using spatiotemporal synchronization

Energy Technology Data Exchange (ETDEWEB)

Tao, Chao [Department of Surgery, Division of Otolaryngology Head and Neck Surgery, University of Wisconsin Medical School, Madison, WI 53792-7375 (United States); Jiang, Jack J. [Department of Surgery, Division of Otolaryngology Head and Neck Surgery, University of Wisconsin Medical School, Madison, WI 53792-7375 (United States)]. E-mail: jiang@surgery.wisc.edu; Zhang, Yu [Department of Surgery, Division of Otolaryngology Head and Neck Surgery, University of Wisconsin Medical School, Madison, WI 53792-7375 (United States)

2007-02-19

A method based on spatiotemporal synchronization is proposed to measure stress distribution in the vocal folds. It is theoretically proved that a measurement system can be synchronized with a vocal fold vibration system by coupling their surface dynamic variables. Therefore, the stress in the vocal folds is predicted by the synchronized continuous model. Numerical experiments are employed to verify this method. The influences of the different coupling variables and the parameter mismatches on stress measurement are also investigated.

Measurement of stress in vocal folds during phonation using spatiotemporal synchronization

International Nuclear Information System (INIS)

Tao, Chao; Jiang, Jack J.; Zhang, Yu

2007-01-01

A method based on spatiotemporal synchronization is proposed to measure stress distribution in the vocal folds. It is theoretically proved that a measurement system can be synchronized with a vocal fold vibration system by coupling their surface dynamic variables. Therefore, the stress in the vocal folds is predicted by the synchronized continuous model. Numerical experiments are employed to verify this method. The influences of the different coupling variables and the parameter mismatches on stress measurement are also investigated

Methods for constructing time synchronous networks. Part 1. Consideration and experiment of time synchronizing functions and devices; Zenkei jikoku dokimo no kosei shuho. 1. Jikoku doki hoshiki no kino kento to jikkenteki kensho

Energy Technology Data Exchange (ETDEWEB)

Serizawa, Y.; Kitamura, K.; Myojin, M.; Shimizu, K. [Central Research Institute of Electric Power Industry, Tokyo (Japan); Nenohi, H.; Morimitsu, M.; Masui, O.; Matsushima, T. [NEC Corp., Tokyo (Japan)

1996-03-01

For the purpose of the back-up protection of regional power line system and the protection and control of accident influence, construction methods of time synchronizing network have been investigated. This paper proposes a method suitable for business power communication. For the synchronization between stations, transmission delay and its fluctuation have to be measured accurately by transmitting time signals between stations. Based on the observed delay values, the function of time correction (phase synchronizing control) of synchronized station is required. A mutual type synchronizing method was proposed, to which a sampling synchronization method of carrier relay system for transmission line protection was applied. In this method, transmission of time signals and measurement of delays are mutually conducted between stations, and phases of independent transmitters of the both stations are controlled so as to be equivalent. This method is characterized by the suppression of delays with fluctuation in the same direction of two-way transmission. For the transmission of time signals, two types of synchronizing devices were employed, i.e., synchronous and asynchronous manners. In the former, frequency synchronous network of SDH (synchronous digital hierarchy) was synchronized. In the latter, a carrier relay device was utilized independent of frequency synchronous network. It was expected that a synchronous network with an order of {mu}s can be constructed. 11 refs., 21 figs., 3 tabs.

Approximation methods for the stability analysis of complete synchronization on duplex networks

Science.gov (United States)

Han, Wenchen; Yang, Junzhong

2018-01-01

Recently, the synchronization on multi-layer networks has drawn a lot of attention. In this work, we study the stability of the complete synchronization on duplex networks. We investigate effects of coupling function on the complete synchronization on duplex networks. We propose two approximation methods to deal with the stability of the complete synchronization on duplex networks. In the first method, we introduce a modified master stability function and, in the second method, we only take into consideration the contributions of a few most unstable transverse modes to the stability of the complete synchronization. We find that both methods work well for predicting the stability of the complete synchronization for small networks. For large networks, the second method still works pretty well.

Phase synchronization of non-Abelian oscillators on small-world networks

Energy Technology Data Exchange (ETDEWEB)

Gu, Zhi-Ming [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Zhao, Ming [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Zhou, Tao [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)]. E-mail: zhutou@ustc.edu; Zhu, Chen-Ping [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Wang, Bing-Hong [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China)

2007-02-26

In this Letter, by extending the concept of Kuramoto oscillator to the left-invariant flow on general Lie group, we investigate the generalized phase synchronization on networks. The analyses and simulations of some typical dynamical systems on Watts-Strogatz networks are given, including the n-dimensional torus, the identity component of 3-dimensional general linear group, the special unitary group, and the special orthogonal group. In all cases, the greater disorder of networks will predict better synchronizability, and the small-world effect ensures the global synchronization for sufficiently large coupling strength. The collective synchronized behaviors of many dynamical systems, such as the integrable systems, the two-state quantum systems and the top systems, can be described by the present phase synchronization frame. In addition, it is intuitive that the low-dimensional systems are more easily to synchronize, however, to our surprise, we found that the high-dimensional systems display obviously synchronized behaviors in regular networks, while these phenomena cannot be observed in low-dimensional systems.

Phase synchronization of non-Abelian oscillators on small-world networks

International Nuclear Information System (INIS)

Gu, Zhi-Ming; Zhao, Ming; Zhou, Tao; Zhu, Chen-Ping; Wang, Bing-Hong

2007-01-01

In this Letter, by extending the concept of Kuramoto oscillator to the left-invariant flow on general Lie group, we investigate the generalized phase synchronization on networks. The analyses and simulations of some typical dynamical systems on Watts-Strogatz networks are given, including the n-dimensional torus, the identity component of 3-dimensional general linear group, the special unitary group, and the special orthogonal group. In all cases, the greater disorder of networks will predict better synchronizability, and the small-world effect ensures the global synchronization for sufficiently large coupling strength. The collective synchronized behaviors of many dynamical systems, such as the integrable systems, the two-state quantum systems and the top systems, can be described by the present phase synchronization frame. In addition, it is intuitive that the low-dimensional systems are more easily to synchronize, however, to our surprise, we found that the high-dimensional systems display obviously synchronized behaviors in regular networks, while these phenomena cannot be observed in low-dimensional systems

Sensorimotor synchronization with tempo-changing auditory sequences: Modeling temporal adaptation and anticipation.

Science.gov (United States)

van der Steen, M C Marieke; Jacoby, Nori; Fairhurst, Merle T; Keller, Peter E

2015-11-11

The current study investigated the human ability to synchronize movements with event sequences containing continuous tempo changes. This capacity is evident, for example, in ensemble musicians who maintain precise interpersonal coordination while modulating the performance tempo for expressive purposes. Here we tested an ADaptation and Anticipation Model (ADAM) that was developed to account for such behavior by combining error correction processes (adaptation) with a predictive temporal extrapolation process (anticipation). While previous computational models of synchronization incorporate error correction, they do not account for prediction during tempo-changing behavior. The fit between behavioral data and computer simulations based on four versions of ADAM was assessed. These versions included a model with adaptation only, one in which adaptation and anticipation act in combination (error correction is applied on the basis of predicted tempo changes), and two models in which adaptation and anticipation were linked in a joint module that corrects for predicted discrepancies between the outcomes of adaptive and anticipatory processes. The behavioral experiment required participants to tap their finger in time with three auditory pacing sequences containing tempo changes that differed in the rate of change and the number of turning points. Behavioral results indicated that sensorimotor synchronization accuracy and precision, while generally high, decreased with increases in the rate of tempo change and number of turning points. Simulations and model-based parameter estimates showed that adaptation mechanisms alone could not fully explain the observed precision of sensorimotor synchronization. Including anticipation in the model increased the precision of simulated sensorimotor synchronization and improved the fit of model to behavioral data, especially when adaptation and anticipation mechanisms were linked via a joint module based on the notion of joint internal

Impact of Degraded Communication on Interdependent Power Systems: The Application of Grid Splitting

Directory of Open Access Journals (Sweden)

Di-An Tian

2016-08-01

Full Text Available Communication is increasingly present for managing and controlling critical infrastructures strengthening their cyber interdependencies. In electric power systems, grid splitting is a topical communication-critical application. It amounts to separating a power system into islands in response to an impending instability, e.g., loss of generator synchronism due to a component fault, by appropriately disconnecting transmission lines and grouping synchronous generators. The successful application of grid splitting depends on the communication infrastructure to collect system-wide synchronized measurements and to relay the command to open line switches. Grid splitting may be ineffective if communication is degraded and its outcome may also depend on the system loading conditions. This paper investigates the effects of degraded communication and load variability on grid splitting. To this aim, a communication delay model is coupled with a transient electrical model and applied to the IEEE 39-Bus and the IEEE 118-Bus Test System. Case studies show that the loss of generator synchronism following a fault is mitigated by timely splitting the network into islands. On the other hand, the results show that communication delays and increased network flows can degrade the performance of grid splitting. The developed framework enables the identification of the requirements of the dedicated communication infrastructure for a successful grid-splitting procedure.

Mathematical foundations of hybrid data assimilation from a synchronization perspective

Science.gov (United States)

Penny, Stephen G.

2017-12-01

The state-of-the-art data assimilation methods used today in operational weather prediction centers around the world can be classified as generalized one-way coupled impulsive synchronization. This classification permits the investigation of hybrid data assimilation methods, which combine dynamic error estimates of the system state with long time-averaged (climatological) error estimates, from a synchronization perspective. Illustrative results show how dynamically informed formulations of the coupling matrix (via an Ensemble Kalman Filter, EnKF) can lead to synchronization when observing networks are sparse and how hybrid methods can lead to synchronization when those dynamic formulations are inadequate (due to small ensemble sizes). A large-scale application with a global ocean general circulation model is also presented. Results indicate that the hybrid methods also have useful applications in generalized synchronization, in particular, for correcting systematic model errors.

Characterization of endocrine events during the periestrous period in sheep after estrous synchronization with controlled internal drug release (CIDR) device.

Science.gov (United States)

Van Cleeff, J; Karsch, F J; Padmanabhan, V

1998-01-01

The Controlled Internal Drug Releasing (CIDR) device is an intravaginal pessary containing progesterone (P4) designed for synchronizing estrus in ruminants. To date, there has been little information available on the timing, duration, and quality of the follicular phase after CIDR removal and how those characteristics compare with natural periovulatory endocrine events. The present communication relates the results of methods we used to characterize the endocrine events that followed CIDR synchronization. Breeding-season ewes were given an injection (10 mg) of Lutalyse (PGF2 alpha), and then studied during three consecutive estrous cycles, beginning in the luteal phase after the estrus induced by PGF2 alpha. Cycle 1 estrus was synchronized with 1 CIDR (Type G) inserted for 8 d beginning 10 d after PGF2 alpha. Cycles 2 and 3 were synchronized with two CIDRs for 8 d beginning 10 d after previous CIDR removal. Cycle 1 estrous behavior and serum gonadotropins showed a follicular phase (the interval from CIDR withdrawal to gonadotropin surge [surge] peak) of 38.2 +/- 1.5 hr. Two CIDRs lengthened the interval to 46.2 +/- 1.5 hr (P synchronization concentrated surges within a 24-hr period in 92% of the ewes in Cycles 1 and 2. Cycles 3 ewes were euthanized at estimated luteal, early follicular, late follicular, LH surge, and secondary FSH rise timepoints. Endocrine data and ovaries showed that 88% of the ewes synchronized with two CIDRs were in the predicted stage of the estrous cycle. These data demonstrate that the CIDR device applied during the luteal phase effectively synchronizes estrus and results in a CIDR removal-to-surge interval of similar length to a natural follicular phase.

Synchronization of metronomes

Science.gov (United States)

Pantaleone, James

2002-10-01

Synchronization is a common phenomenon in physical and biological systems. We examine the synchronization of two (and more) metronomes placed on a freely moving base. The small motion of the base couples the pendulums causing synchronization. The synchronization is generally in-phase, with antiphase synchronization occurring only under special conditions. The metronome system provides a mechanical realization of the popular Kuramoto model for synchronization of biological oscillators, and is excellent for classroom demonstrations and an undergraduate physics lab.

Individual gregariousness predicts behavioural synchronization in a foraging herbivore, the sheep (Ovis aries).

Science.gov (United States)

Hauschildt, Verena; Gerken, Martina

2015-04-01

Diversity of animal personalities has been proposed to arise from differences in social attraction, and to enhance behavioural flexibility of a population. The present study evaluated gregariousness as a personality trait in 14 ewes kept on pasture. Gregariousness was defined based on the frequency of having a close neighbour (behaviour was recorded individually every 15 min. Each session lasted 2.5h (08.30-11.00 h or 14.30-17.00 h, respectively). Behavioural synchronization was highest when the group consisted only of HG individuals (κHG=0.69, κLG=0.31; t=5.29; pbehavioural synchronization in sheep. Though sheep are generally recognized as a highly gregarious species, HG and LG individuals could be differentiated clearly and consistently. Research on animal personality might help explain social influences on behavioural synchronization. Copyright © 2015 Elsevier B.V. All rights reserved.

Energy-efficient pulse-coupled synchronization strategy design for wireless sensor networks through reduced idle listening

Science.gov (United States)

Wang, Yongqiang; Núñez, Felipe; Doyle, Francis J.

2013-01-01

Synchronization is crucial to wireless sensor networks due to their decentralized structure. We propose an energy-efficient pulse-coupled synchronization strategy to achieve this goal. The basic idea is to reduce idle listening by intentionally introducing a large refractory period in the sensors’ cooperation. The large refractory period greatly reduces idle listening in each oscillation period, and is analytically proven to have no influence on the time to synchronization. Hence, it significantly reduces the total energy consumption in a synchronization process. A topology control approach tailored for pulse-coupled synchronization is given to guarantee a k-edge strongly connected interaction topology, which is tolerant to communication-link failures. The topology control approach is totally decentralized and needs no information exchange among sensors, and it is applicable to dynamic network topologies as well. This facilitates a completely decentralized implementation of the synchronization strategy. The strategy is applicable to mobile sensor networks, too. QualNet case studies confirm the effectiveness of the synchronization strategy. PMID:24307831

Event-triggered synchronization for reaction-diffusion complex networks via random sampling

Science.gov (United States)

Dong, Tao; Wang, Aijuan; Zhu, Huiyun; Liao, Xiaofeng

2018-04-01

In this paper, the synchronization problem of the reaction-diffusion complex networks (RDCNs) with Dirichlet boundary conditions is considered, where the data is sampled randomly. An event-triggered controller based on the sampled data is proposed, which can reduce the number of controller and the communication load. Under this strategy, the synchronization problem of the diffusion complex network is equivalently converted to the stability of a of reaction-diffusion complex dynamical systems with time delay. By using the matrix inequality technique and Lyapunov method, the synchronization conditions of the RDCNs are derived, which are dependent on the diffusion term. Moreover, it is found the proposed control strategy can get rid of the Zeno behavior naturally. Finally, a numerical example is given to verify the obtained results.

Synchronizing and controlling hyperchaos in complex Lorentz-Haken systems

International Nuclear Information System (INIS)

Fang Jinqing

1995-03-01

Synchronizing hyperchaos is realized by the drive-response relationship in the complex Lorentz-Haken system and its higher-order cascading systems for the first time. Controlling hyperchaos is achieved by the intermittent proportional feedback to all of the drive (master) system variables. The complex Lorentz-Haken system describes the detuned single-mode laser and is taken as a typical example of hyperchaotic synchronization to clarify our ideas and results. The ideas and concepts could be extended to some nonlinear dynamical systems and have prospects for potential applications, for example. to laser, electronics, plasma, cryptography, communication, chemical and biological systems and so on. (8 figs., 2 tabs.)

Synchronizing and controlling hyperchaos in complex Lorentz-Haken systems

Energy Technology Data Exchange (ETDEWEB)

Jinqing, Fang [Academia Sinica, Beijing, BJ (China). Inst. of Atomic Energy

1995-03-01

Synchronizing hyperchaos is realized by the drive-response relationship in the complex Lorentz-Haken system and its higher-order cascading systems for the first time. Controlling hyperchaos is achieved by the intermittent proportional feedback to all of the drive (master) system variables. The complex Lorentz-Haken system describes the detuned single-mode laser and is taken as a typical example of hyperchaotic synchronization to clarify our ideas and results. The ideas and concepts could be extended to some nonlinear dynamical systems and have prospects for potential applications, for example. to laser, electronics, plasma, cryptography, communication, chemical and biological systems and so on. (8 figs., 2 tabs.).

Synchronous activity in cat visual cortex encodes collinear and cocircular contours.

Science.gov (United States)

Samonds, Jason M; Zhou, Zhiyi; Bernard, Melanie R; Bonds, A B

2006-04-01

We explored how contour information in primary visual cortex might be embedded in the simultaneous activity of multiple cells recorded with a 100-electrode array. Synchronous activity in cat visual cortex was more selective and predictable in discriminating between drifting grating and concentric ring stimuli than changes in firing rate. Synchrony was found even between cells with wholly different orientation preferences when their receptive fields were circularly aligned, and membership in synchronous groups was orientation and curvature dependent. The existence of synchrony between cocircular cells reinforces its role as a general mechanism for contour integration and shape detection as predicted by association field concepts. Our data suggest that cortical synchrony results from common and synchronous input from earlier visual areas and that it could serve to shape extrastriate response selectivity.

Impact of delays on the synchronization transitions of modular neuronal networks with hybrid synapses

Science.gov (United States)

Liu, Chen; Wang, Jiang; Yu, Haitao; Deng, Bin; Wei, Xile; Tsang, Kaiming; Chan, Wailok

2013-09-01

The combined effects of the information transmission delay and the ratio of the electrical and chemical synapses on the synchronization transitions in the hybrid modular neuronal network are investigated in this paper. Numerical results show that the synchronization of neuron activities can be either promoted or destroyed as the information transmission delay increases, irrespective of the probability of electrical synapses in the hybrid-synaptic network. Interestingly, when the number of the electrical synapses exceeds a certain level, further increasing its proportion can obviously enhance the spatiotemporal synchronization transitions. Moreover, the coupling strength has a significant effect on the synchronization transition. The dominated type of the synapse always has a more profound effect on the emergency of the synchronous behaviors. Furthermore, the results of the modular neuronal network structures demonstrate that excessive partitioning of the modular network may result in the dramatic detriment of neuronal synchronization. Considering that information transmission delays are inevitable in intra- and inter-neuronal networks communication, the obtained results may have important implications for the exploration of the synchronization mechanism underlying several neural system diseases such as Parkinson's Disease.

Dynamical noise filter and conditional entropy analysis in chaos synchronization.

Science.gov (United States)

Wang, Jiao; Lai, C-H

2006-06-01

It is shown that, in a chaotic synchronization system whose driving signal is exposed to channel noise, the estimation of the drive system states can be greatly improved by applying the dynamical noise filtering to the response system states. If the noise is bounded in a certain range, the estimation errors, i.e., the difference between the filtered responding states and the driving states, can be made arbitrarily small. This property can be used in designing an alternative digital communication scheme. An analysis based on the conditional entropy justifies the application of dynamical noise filtering in generating quality synchronization.

Combining Synchronous and Asynchronous Collaboration within 3D City Models

Science.gov (United States)

Klimke, Jan; Döllner, Jürgen

This paper presents an approach for combining spatially distributed synchronous and asynchronous collaboration within 3D city models. Software applications use these models as additional communication medium to facilitate communication of georeferenced and geospatial information. Collaboration tools should support both the communication with other collaborators and their awareness of the current collaboration context. To support collaborative knowledge construction and gathering, we have designed a collaboration system to facilitate (a) creation of annotations that have 3D references to the virtual 3D city model and (b) collection information about the context in which these annotations are created. Our approach supports synchronous collaboration in connection with the creation of non volatile, precisely georeferenced units of information allow for a comprehensible form of cooperation in spatially distributed settings. Storage and retrieval of this information is provided through a Web Feature Service, which eases integration of collaboration data into existing applications. We further introduce a visualization technique that integrates annotations as complex structured data into the 3D visualization. This avoids media breaks and disruptions in working processes and creates a spatial coherence between annotation and annotated feature or geometry.

Synchronization among Mechanisms of Renal Autoregulation is Reduced in Hypertensive Rats

DEFF Research Database (Denmark)

Sosnovtseva, Olga; Pavlov, A. N.; Mosekilde, Erik

2007-01-01

, and a slower (20-40 mHz) oscillation in tubuloglomerular feedback (TGF). These mechanisms interact; the TGF mode modulates both the amplitude and the frequency of the myogenic mode. Nephrons also communicate with each other using vascular signals triggered by membrane events in arteriolar smooth muscle cells...... in SHR is a state of partial synchronization with entrainment between neighboring nephrons for only one of the modes. Modulation of the myogenic mode by the TGF mode is much stronger in hypertensive than in normotensive rats. Synchronization among nephrons forms the basis for an integrated reaction...

Enhancing performance of next generation FSO communication systems using soft computing-based predictions.

Science.gov (United States)

Kazaura, Kamugisha; Omae, Kazunori; Suzuki, Toshiji; Matsumoto, Mitsuji; Mutafungwa, Edward; Korhonen, Timo O; Murakami, Tadaaki; Takahashi, Koichi; Matsumoto, Hideki; Wakamori, Kazuhiko; Arimoto, Yoshinori

2006-06-12

The deterioration and deformation of a free-space optical beam wave-front as it propagates through the atmosphere can reduce the link availability and may introduce burst errors thus degrading the performance of the system. We investigate the suitability of utilizing soft-computing (SC) based tools for improving performance of free-space optical (FSO) communications systems. The SC based tools are used for the prediction of key parameters of a FSO communications system. Measured data collected from an experimental FSO communication system is used as training and testing data for a proposed multi-layer neural network predictor (MNNP) used to predict future parameter values. The predicted parameters are essential for reducing transmission errors by improving the antenna's accuracy of tracking data beams. This is particularly essential for periods considered to be of strong atmospheric turbulence. The parameter values predicted using the proposed tool show acceptable conformity with original measurements.

A satellite mobile communication system based on Band-Limited Quasi-Synchronous Code Division Multiple Access (BLQS-CDMA)

Science.gov (United States)

Degaudenzi, R.; Elia, C.; Viola, R.

1990-01-01

Discussed here is a new approach to code division multiple access applied to a mobile system for voice (and data) services based on Band Limited Quasi Synchronous Code Division Multiple Access (BLQS-CDMA). The system requires users to be chip synchronized to reduce the contribution of self-interference and to make use of voice activation in order to increase the satellite power efficiency. In order to achieve spectral efficiency, Nyquist chip pulse shaping is used with no detection performance impairment. The synchronization problems are solved in the forward link by distributing a master code, whereas carrier forced activation and closed loop control techniques have been adopted in the return link. System performance sensitivity to nonlinear amplification and timing/frequency synchronization errors are analyzed.

Understanding Eating Behaviors through Parental Communication and the Integrative Model of Behavioral Prediction.

Science.gov (United States)

Scheinfeld, Emily; Shim, Minsun

2017-05-01

Emerging adulthood (EA) is an important yet overlooked period for developing long-term health behaviors. During these years, emerging adults adopt health behaviors that persist throughout life. This study applies the Integrative Model of Behavioral Prediction (IMBP) to examine the role of childhood parental communication in predicting engagement in healthful eating during EA. Participants included 239 college students, ages 18 to 25, from a large university in the southern United States. Participants were recruited and data collection occurred spring 2012. Participants responded to measures to assess perceived parental communication, eating behaviors, attitudes, subjective norms, and behavioral control over healthful eating. SEM and mediation analyses were used to address the hypotheses posited. Data demonstrated that perceived parent-child communication - specifically, its quality and target-specific content - significantly predicted emerging adults' eating behaviors, mediated through subjective norm and perceived behavioral control. This study sets the stage for further exploration and understanding of different ways parental communication influences emerging adults' healthy behavior enactment.

Decentralized Model Predictive Control for Cooperative Multiple Vehicles Subject to Communication Loss

Directory of Open Access Journals (Sweden)

Hojjat A. Izadi

2011-01-01

Full Text Available The decentralized model predictive control (DMPC of multiple cooperative vehicles with the possibility of communication loss/delay is investigated. The neighboring vehicles exchange their predicted trajectories at every sample time to maintain the cooperation objectives. In the event of a communication loss (packet dropout, the most recent available information, which is potentially delayed, is used. Then the communication loss problem changes to a cooperative problem when random large communication delays are present. Such large communication delays can lead to poor cooperation performance and unsafe behaviors such as collisions. A new DMPC approach is developed to improve the cooperation performance and achieve safety in the presence of the large communication delays. The proposed DMPC architecture estimates the tail of neighbor's trajectory which is not available due to the large communication delays for improving the performance. The concept of the tube MPC is also employed to provide the safety of the fleet against collisions, in the presence of large intervehicle communication delays. In this approach, a tube shaped trajectory set is assumed around the trajectory of the neighboring vehicles whose trajectory is delayed/lost. The radius of tube is a function of the communication delay and vehicle's maneuverability (in the absence of model uncertainty. The simulation of formation problem of multiple vehicles is employed to illustrate the effectiveness of the proposed approach.

Adaptive Synchronization for Heterogeneous Multi-Agent Systems with Switching Topologies

Directory of Open Access Journals (Sweden)

Muhammad Ridho Rosa

2018-02-01

Full Text Available This work provides a multi-agent extension of output-feedback model reference adaptive control (MRAC, designed to synchronize a network of heterogeneous uncertain agents. The implementation of this scheme is based on multi-agent matching conditions. The practical advantage of the proposed MRAC is the possibility of handling the case of the unknown dynamics of the agents only by using the output and the control input of its neighbors. In addition, it is reasonable to consider the case when the communication topology is time-varying. In this work, the time-varying communication leads to a switching control structure that depends on the number of the predecessor of the agents. By using the switching control structure to handle the time-varying topologies, we show that synchronization can be achieved. The multi-agent adaptive switching controller is first analyzed, and numerical simulations based on formation control of simplifier quadcopter dynamics are provided.

A General Design Methodology for Synchronous Early-Completion-Prediction Adders in Nano-CMOS DSP Architectures

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Mauro Olivieri

2013-01-01

Full Text Available Synchronous early-completion-prediction adders (ECPAs are used for high clock rate and high-precision DSP datapaths, as they allow a dominant amount of single-cycle operations even if the worst-case carry propagation delay is longer than the clock period. Previous works have also demonstrated ECPA advantages for average leakage reduction and NBTI effects reduction in nanoscale CMOS technologies. This paper illustrates a general systematic methodology to design ECPA units, targeting nanoscale CMOS technologies, which is not available in the current literature yet. The method is fully compatible with standard VLSI macrocell design tools and standard adder structures and includes automatic definition of critical test patterns for postlayout verification. A design example is included, reporting speed and power data superior to previous works.

Phase-response curves and synchronized neural networks.

Science.gov (United States)

Smeal, Roy M; Ermentrout, G Bard; White, John A

2010-08-12

We review the principal assumptions underlying the application of phase-response curves (PRCs) to synchronization in neuronal networks. The PRC measures how much a given synaptic input perturbs spike timing in a neural oscillator. Among other applications, PRCs make explicit predictions about whether a given network of interconnected neurons will synchronize, as is often observed in cortical structures. Regarding the assumptions of the PRC theory, we conclude: (i) The assumption of noise-tolerant cellular oscillations at or near the network frequency holds in some but not all cases. (ii) Reduced models for PRC-based analysis can be formally related to more realistic models. (iii) Spike-rate adaptation limits PRC-based analysis but does not invalidate it. (iv) The dependence of PRCs on synaptic location emphasizes the importance of improving methods of synaptic stimulation. (v) New methods can distinguish between oscillations that derive from mutual connections and those arising from common drive. (vi) It is helpful to assume linear summation of effects of synaptic inputs; experiments with trains of inputs call this assumption into question. (vii) Relatively subtle changes in network structure can invalidate PRC-based predictions. (viii) Heterogeneity in the preferred frequencies of component neurons does not invalidate PRC analysis, but can annihilate synchronous activity.

Synchronization of coupled different chaotic FitzHugh-Nagumo neurons with unknown parameters under communication-direction-dependent coupling.

Science.gov (United States)

Iqbal, Muhammad; Rehan, Muhammad; Khaliq, Abdul; Saeed-ur-Rehman; Hong, Keum-Shik

2014-01-01

This paper investigates the chaotic behavior and synchronization of two different coupled chaotic FitzHugh-Nagumo (FHN) neurons with unknown parameters under external electrical stimulation (EES). The coupled FHN neurons of different parameters admit unidirectional and bidirectional gap junctions in the medium between them. Dynamical properties, such as the increase in synchronization error as a consequence of the deviation of neuronal parameters for unlike neurons, the effect of difference in coupling strengths caused by the unidirectional gap junctions, and the impact of large time-delay due to separation of neurons, are studied in exploring the behavior of the coupled system. A novel integral-based nonlinear adaptive control scheme, to cope with the infeasibility of the recovery variable, for synchronization of two coupled delayed chaotic FHN neurons of different and unknown parameters under uncertain EES is derived. Further, to guarantee robust synchronization of different neurons against disturbances, the proposed control methodology is modified to achieve the uniformly ultimately bounded synchronization. The parametric estimation errors can be reduced by selecting suitable control parameters. The effectiveness of the proposed control scheme is illustrated via numerical simulations.

Distributed neural network control for adaptive synchronization of uncertain dynamical multiagent systems.

Science.gov (United States)

Peng, Zhouhua; Wang, Dan; Zhang, Hongwei; Sun, Gang

2014-08-01

This paper addresses the leader-follower synchronization problem of uncertain dynamical multiagent systems with nonlinear dynamics. Distributed adaptive synchronization controllers are proposed based on the state information of neighboring agents. The control design is developed for both undirected and directed communication topologies without requiring the accurate model of each agent. This result is further extended to the output feedback case where a neighborhood observer is proposed based on relative output information of neighboring agents. Then, distributed observer-based synchronization controllers are derived and a parameter-dependent Riccati inequality is employed to prove the stability. This design has a favorable decouple property between the observer and the controller designs for nonlinear multiagent systems. For both cases, the developed controllers guarantee that the state of each agent synchronizes to that of the leader with bounded residual errors. Two illustrative examples validate the efficacy of the proposed methods.

Phase synchronization on small-world networks with community structure

International Nuclear Information System (INIS)

Xiao-Hua, Wang; Li-Cheng, Jiao; Jian-She, Wu

2010-01-01

In this paper, we propose a simple model that can generate small-world network with community structure. The network is introduced as a tunable community organization with parameter r, which is directly measured by the ratio of inter- to intra-community connectivity, and a smaller r corresponds to a stronger community structure. The structure properties, including the degree distribution, clustering, the communication efficiency and modularity are also analysed for the network. In addition, by using the Kuramoto model, we investigated the phase synchronization on this network, and found that increasing the fuzziness of community structure will markedly enhance the network synchronizability; however, in an abnormal region (r ≤ 0.001), the network has even worse synchronizability than the case of isolated communities (r = 0). Furthermore, this network exhibits a remarkable synchronization behaviour in topological scales: the oscillators of high densely interconnected communities synchronize more easily, and more rapidly than the whole network. (general)

Shuttle bit rate synchronizer. [signal to noise ratios and error analysis

Science.gov (United States)

Huey, D. C.; Fultz, G. L.

1974-01-01

A shuttle bit rate synchronizer brassboard unit was designed, fabricated, and tested, which meets or exceeds the contractual specifications. The bit rate synchronizer operates at signal-to-noise ratios (in a bit rate bandwidth) down to -5 dB while exhibiting less than 0.6 dB bit error rate degradation. The mean acquisition time was measured to be less than 2 seconds. The synchronizer is designed around a digital data transition tracking loop whose phase and data detectors are integrate-and-dump filters matched to the Manchester encoded bits specified. It meets the reliability (no adjustments or tweaking) and versatility (multiple bit rates) of the shuttle S-band communication system through an implementation which is all digital after the initial stage of analog AGC and A/D conversion.

Synchronization of the unified chaotic systems using a sliding mode controller

International Nuclear Information System (INIS)

Zribi, Mohamed; Smaoui, Nejib; Salim, Haitham

2009-01-01

The unified chaotic system incorporates the behaviors of the Lorenz, the Chen and the Lue chaotic systems. This paper deals with the synchronization of two identical unified chaotic systems where the slave system is assumed to have a single input. A sliding mode controller is proposed to synchronize the two systems. The asymptotic convergence to zero of the errors between the states of the master and the slave systems is shown. Simulations results are presented to illustrate the proposed controller; they indicate that the designed controller is able to synchronize the unified chaotic systems. Also, simulation results show that the proposed control scheme is robust to random bounded disturbances acting on the master system. Moreover, the proposed scheme is applied to the secure communications field, where simulation results indicate that the proposed scheme is effective.

Trust and Understanding in Face-to-Face and Synchronous Online Negotiations

NARCIS (Netherlands)

van der Toorn, Yvonne; van der Wijst, Per; Damen, Debby; van Amelsvoort, Marije; Zaraté, P.; Camilleri, G.; Kamissoko, D.; Amblard, F.

This study investigates to what extent the synchronous character of chat communication overcomes the problems in creating mutual understanding and trust between conflicting parties. An experimental study was conducted in which participants negotiated with a confederate in either a face-to-face or

The Role of Leadership in Self-Synchronized Operations - Implications for the U.S. Military

National Research Council Canada - National Science Library

Still, Bryan

2003-01-01

.... It identifies three leadership skills essential to self-synchronized operations the ability to delegate authority, the ability to communicate a clear commander's intent, and the ability to tolerate...

Synchronizing strict-feedback and general strict-feedback chaotic systems via a single controller

International Nuclear Information System (INIS)

Chen Shihua; Wang Feng; Wang Changping

2004-01-01

We present a systematic design procedure to synchronize a class of chaotic systems in a so-called strict-feedback form based on back-stepping procedure. This approach needs only a single controller to realize synchronization no matter how many dimensions the chaotic system contains. Furthermore, we point out that the method does not work for general strict-feedback chaotic systems, for instance, Lorenz system. Therefore, we propose three kinds of synchronization schemes for Lorenz system using the Lyapunov function method. All the three schemes avoid including divergence factor as in Ref. [Chaos, Solitons and Fractals 16 (2003) 37]. Especially in the last two schemes, we need only one state variable in controller, which has important significance in chaos synchronization used for communication purposes. Finally numerical simulations are provided to show the effectiveness and feasibility of the developed methods

Complete synchronization condition in a network of piezoelectric micro-beam

International Nuclear Information System (INIS)

Taffoti Yolong, V.Y.; Woafo, P.

2007-10-01

This work deals with the dynamics of a network of piezoelectric micro-beams. The complete synchronization condition for this class of chaotic nonlinear electromechanical systems devices with nearest-neighbor diffusive coupling is studied. The nonlinearities on the device studied here are both on the electrical component and on the mechanical one. The investigation is made for the case of a large number of discrete piezoelectric disks coupled. The problem of chaos synchronization is described and converted into the analysis of stability of the system via its differential equations. We show that the complete synchronization of N identical coupled nonlinear chaotic systems having the shift invariant coupling schemes can be calculated from the synchronization of two of them coupled in both directions. According to analytical, semi-analytical predictions and numerical calculations, the transition boundaries for chaos synchronization state in the coupled system are determined as a function of the increasing number of oscillators. (author)

Communication through resonance in spiking neuronal networks.

Science.gov (United States)

Hahn, Gerald; Bujan, Alejandro F; Frégnac, Yves; Aertsen, Ad; Kumar, Arvind

2014-08-01

The cortex processes stimuli through a distributed network of specialized brain areas. This processing requires mechanisms that can route neuronal activity across weakly connected cortical regions. Routing models proposed thus far are either limited to propagation of spiking activity across strongly connected networks or require distinct mechanisms that create local oscillations and establish their coherence between distant cortical areas. Here, we propose a novel mechanism which explains how synchronous spiking activity propagates across weakly connected brain areas supported by oscillations. In our model, oscillatory activity unleashes network resonance that amplifies feeble synchronous signals and promotes their propagation along weak connections ("communication through resonance"). The emergence of coherent oscillations is a natural consequence of synchronous activity propagation and therefore the assumption of different mechanisms that create oscillations and provide coherence is not necessary. Moreover, the phase-locking of oscillations is a side effect of communication rather than its requirement. Finally, we show how the state of ongoing activity could affect the communication through resonance and propose that modulations of the ongoing activity state could influence information processing in distributed cortical networks.

Synchronization of Coupled Different Chaotic FitzHugh-Nagumo Neurons with Unknown Parameters under Communication-Direction-Dependent Coupling

Directory of Open Access Journals (Sweden)

Muhammad Iqbal

2014-01-01

Full Text Available This paper investigates the chaotic behavior and synchronization of two different coupled chaotic FitzHugh-Nagumo (FHN neurons with unknown parameters under external electrical stimulation (EES. The coupled FHN neurons of different parameters admit unidirectional and bidirectional gap junctions in the medium between them. Dynamical properties, such as the increase in synchronization error as a consequence of the deviation of neuronal parameters for unlike neurons, the effect of difference in coupling strengths caused by the unidirectional gap junctions, and the impact of large time-delay due to separation of neurons, are studied in exploring the behavior of the coupled system. A novel integral-based nonlinear adaptive control scheme, to cope with the infeasibility of the recovery variable, for synchronization of two coupled delayed chaotic FHN neurons of different and unknown parameters under uncertain EES is derived. Further, to guarantee robust synchronization of different neurons against disturbances, the proposed control methodology is modified to achieve the uniformly ultimately bounded synchronization. The parametric estimation errors can be reduced by selecting suitable control parameters. The effectiveness of the proposed control scheme is illustrated via numerical simulations.

Doing synchronous online focus groups with young people: methodological reflections.

Science.gov (United States)

Fox, Fiona E; Morris, Marianne; Rumsey, Nichola

2007-04-01

Although online focus groups are emerging as a worthwhile methodological approach for qualitative researchers, reporting has been constrained in several ways. The majority of studies report asynchronous groups, whereas others employ synchronous exchanges, the efficacy of which with young people has seldom been explored. Considering the popularity of the Internet as a communication tool for young people, this missed opportunity is surprising. Based on a series of synchronous online focus groups with young people, the authors explore why this approach might be an effective way of engaging young people with appearance-related concerns in research. In this article, they discuss the process of hosting and moderating synchronous online focus groups, highlighting some of the ethical, pragmatic, and personal challenges that might face researchers using this method. Through a reflexive approach, they intend to inform and encourage qualitative researchers to consider alternative ways of engaging young people in research.

Prediction of parent artery of anterior communicating artery aneurysm on CT angiography

International Nuclear Information System (INIS)

Chung, Jin Young; Han, Tae Il; Kim, Dae Hong; Han, Hyun Young; Kim, Hyun Jung; Song, Mun Kab

1999-01-01

To determine whether CT angiography can predict the parent artery of an anterior communicating aneurysm on the basis of characteristics of the aneurysm and precommunication anterior cerebral artery. Eighteen patients with anterior communication aneurysm were studied prospectively using CT angiography and conventional angiography. The parent artery of an aneurysm was predicted by evaluating aneurysm neck location, direction of aneurysm projection, and size of the precommunicating anterior cerebral artery, as seen on CT angiography. A somatom Plus-4 spiral CT scanner was used and shaded-surface display three-dimensional images were constructed. Aneurysm neck was located near the parent artery in 12 cases(66.7%), and aneurysm projection was against the parent artery in 11 cases(61.1%). The parent artery of the anterior cerebral artery was larger in 15 cases(83.3%), including ten cases of hypoplasia or agenesis of the contralateral anterior cerebral artery. In 17 of 18 aneurysms(94.4%) the parent artery seen on DSA was correctly predicted by CT angiography. The parent artery of an anterior communicating aneurysm can be predicted by evaluating aneurysm neck location, direction of aneurysm projection, and precommunicating anterior cerebral artery, as seen on CT angiography

Evaluating the importance of social motor synchronization and motor skill for understanding autism.

Science.gov (United States)

Fitzpatrick, Paula; Romero, Veronica; Amaral, Joseph L; Duncan, Amie; Barnard, Holly; Richardson, Michael J; Schmidt, R C

2017-10-01

Impairments in social interaction and communicating with others are core features of autism spectrum disorder (ASD), but the specific processes underlying such social competence impairments are not well understood. An important key for increasing our understanding of ASD-specific social deficits may lie with the social motor synchronization that takes place when we implicitly coordinate our bodies with others. Here, we tested whether dynamical measures of synchronization differentiate children with ASD from controls and further explored the relationships between synchronization ability and motor control problems. We found (a) that children with ASD exhibited different and less stable patterns of social synchronization ability than controls; (b) children with ASD performed motor movements that were slower and more variable in both spacing and timing; and (c) some social synchronization that involved motor timing was related to motor ability but less rhythmic synchronization was not. These findings raise the possibility that objective dynamical measures of synchronization ability and motor skill could provide new insights into understanding the social deficits in ASD that could ultimately aid clinical diagnosis and prognosis. Autism Res 2017, 10: 1687-1699. © 2017 International Society for Autism Research, Wiley Periodicals, Inc. © 2017 International Society for Autism Research, Wiley Periodicals, Inc.

Synchronous communication in PLM environments using annotated CAD models

OpenAIRE

Camba, Jorge D.; Contero, Manuel; Salvador Herranz, Gustavo Manuel; Plumed, Raquel

2016-01-01

The connection of resources, data, and knowledge through communication technology plays a vital role in current collaborative design methodologies and Product Lifecycle Management (PLM) systems, as these elements act as channels for information and meaning. Despite significant advances in the area of PLM, most communication tools are used as separate services that are disconnected from existing development environments. Consequently, during a communication session, the specific elements being...

Dynamic eccentricity fault diagnosis in round rotor synchronous motors

International Nuclear Information System (INIS)

Ebrahimi, Bashir Mahdi; Etemadrezaei, Mohammad; Faiz, Jawad

2011-01-01

Research highlights: → We have presented a novel approach to detect dynamic eccentricity in round rotor synchronous motors. → We have introduced an efficient index based on processing torque using time series data mining method. → The stator current spectrum of the motor under different levels of fault and load are computed. → Winding function method has been employed to model healthy and faulty synchronous motors. -- Abstract: In this paper, a novel approach is presented to detect dynamic eccentricity in round rotor synchronous motors. For this, an efficient index is introduced based on processing developed torque using time series data mining (TSDM) method. This index can be utilized to diagnose eccentricity fault and its degree. The capability of this index to predict dynamic eccentricity is illustrated by investigation of load variation impacts on the nominated index. Stator current spectrum of the faulty synchronous motor under different loads and dynamic eccentricity degrees are computed. Effects of the dynamic eccentricity and load variation simultaneously are scrutinized on the magnitude of 17th and 19th harmonic components as traditional indices for eccentricity fault diagnosis in synchronous motors. Necessity signals and parameters for processing and feature extraction are evaluated by winding function method which is employed to model healthy and faulty synchronous motors.

Communication and synchronization aspects of a mixed hardware control and data acquisition system

International Nuclear Information System (INIS)

Schmidt, V.; Flor, G.; Luchetta, A.; Manduchi, G.; Piacentini, I.E.; Vitturi, S.; Hemming, O.N.

1989-01-01

The paper deals with some specific aspects of the control and data acquisition system of the RFX nuclear fusion experiment, at present under construction in Padova, Italy. This system is built around a local area network which connects programmable controllers, minicomputers with CAMAC front-end, and personal computers as operator consoles. These three types of nodes use compatible software which contain a set of low level routines according to levels one to four of the ISO OSI recommendations. The paper describes in detail how the overall system synchronization is achieved. Another aspect described in the paper is the proposed solution for the precision timing and waveform generation (which uses commercial CAMAC hardware) and its integration with the overall system synchronization

Sensitivity to synchronicity of biological motion in normal and amblyopic vision

Science.gov (United States)

Luu, Jennifer Y.; Levi, Dennis M.

2017-01-01

Amblyopia is a developmental disorder of spatial vision that results from abnormal early visual experience usually due to the presence of strabismus, anisometropia, or both strabismus and anisometropia. Amblyopia results in a range of visual deficits that cannot be corrected by optics because the deficits reflect neural abnormalities. Biological motion refers to the motion patterns of living organisms, and is normally displayed as points of lights positioned at the major joints of the body. In this experiment, our goal was twofold. We wished to examine whether the human visual system in people with amblyopia retained the higher-level processing capabilities to extract visual information from the synchronized actions of others, therefore retaining the ability to detect biological motion. Specifically, we wanted to determine if the synchronized interaction of two agents performing a dancing routine allowed the amblyopic observer to use the actions of one agent to predict the expected actions of a second agent. We also wished to establish whether synchronicity sensitivity (detection of synchronized versus desynchronized interactions) is impaired in amblyopic observers relative to normal observers. The two aims are differentiated in that the first aim looks at whether synchronized actions result in improved expected action predictions while the second aim quantitatively compares synchronicity sensitivity, or the ratio of desynchronized to synchronized detection sensitivities, to determine if there is a difference between normal and amblyopic observers. Our results show that the ability to detect biological motion requires more samples in both eyes of amblyopes than in normal control observers. The increased sample threshold is not the result of low-level losses but may reflect losses in feature integration due to undersampling in the amblyopic visual system. However, like normal observers, amblyopes are more sensitive to synchronized versus desynchronized interactions

Robust Adaptive Synchronization of Ring Configured Uncertain Chaotic FitzHugh–Nagumo Neurons under Direction-Dependent Coupling

Directory of Open Access Journals (Sweden)

Muhammad Iqbal

2018-02-01

Full Text Available This paper exploits the dynamical modeling, behavior analysis, and synchronization of a network of four different FitzHugh–Nagumo (FHN neurons with unknown parameters linked in a ring configuration under direction-dependent coupling. The main purpose is to investigate a robust adaptive control law for the synchronization of uncertain and perturbed neurons, communicating in a medium of bidirectional coupling. The neurons are assumed to be different and interconnected in a ring structure. The strength of the gap junctions is taken to be different for each link in the network, owing to the inter-neuronal coupling medium properties. Robust adaptive control mechanism based on Lyapunov stability analysis is employed and theoretical criteria are derived to realize the synchronization of the network of four FHN neurons in a ring form with unknown parameters under direction-dependent coupling and disturbances. The proposed scheme for synchronization of dissimilar neurons, under external electrical stimuli, coupled in a ring communication topology, having all parameters unknown, and subject to directional coupling medium and perturbations, is addressed for the first time as per our knowledge. To demonstrate the efficacy of the proposed strategy, simulation results are provided.

Robust Adaptive Synchronization of Ring Configured Uncertain Chaotic FitzHugh–Nagumo Neurons under Direction-Dependent Coupling

Science.gov (United States)

Iqbal, Muhammad; Rehan, Muhammad; Hong, Keum-Shik

2018-01-01

This paper exploits the dynamical modeling, behavior analysis, and synchronization of a network of four different FitzHugh–Nagumo (FHN) neurons with unknown parameters linked in a ring configuration under direction-dependent coupling. The main purpose is to investigate a robust adaptive control law for the synchronization of uncertain and perturbed neurons, communicating in a medium of bidirectional coupling. The neurons are assumed to be different and interconnected in a ring structure. The strength of the gap junctions is taken to be different for each link in the network, owing to the inter-neuronal coupling medium properties. Robust adaptive control mechanism based on Lyapunov stability analysis is employed and theoretical criteria are derived to realize the synchronization of the network of four FHN neurons in a ring form with unknown parameters under direction-dependent coupling and disturbances. The proposed scheme for synchronization of dissimilar neurons, under external electrical stimuli, coupled in a ring communication topology, having all parameters unknown, and subject to directional coupling medium and perturbations, is addressed for the first time as per our knowledge. To demonstrate the efficacy of the proposed strategy, simulation results are provided. PMID:29535622

Overview of Cell Synchronization.

Science.gov (United States)

Banfalvi, Gaspar

2017-01-01

The widespread interest in cell synchronization is maintained by the studies of control mechanism involved in cell cycle regulation. During the synchronization distinct subpopulations of cells are obtained representing different stages of the cell cycle. These subpopulations are then used to study regulatory mechanisms of the cycle at the level of macromolecular biosynthesis (DNA synthesis, gene expression, protein synthesis), protein phosphorylation, development of new drugs, etc. Although several synchronization methods have been described, it is of general interest that scientists get a compilation and an updated view of these synchronization techniques. This introductory chapter summarizes: (1) the basic concepts and principal criteria of cell cycle synchronizations, (2) the most frequently used synchronization methods, such as physical fractionation (flow cytometry, dielectrophoresis, cytofluorometric purification), chemical blockade, (3) synchronization of embryonic cells, (4) synchronization at low temperature, (5) comparison of cell synchrony techniques, (6) synchronization of unicellular organisms, and (7) the effect of synchronization on transfection.

SPEEDES - A multiple-synchronization environment for parallel discrete-event simulation

Science.gov (United States)

Steinman, Jeff S.

1992-01-01

Synchronous Parallel Environment for Emulation and Discrete-Event Simulation (SPEEDES) is a unified parallel simulation environment. It supports multiple-synchronization protocols without requiring users to recompile their code. When a SPEEDES simulation runs on one node, all the extra parallel overhead is removed automatically at run time. When the same executable runs in parallel, the user preselects the synchronization algorithm from a list of options. SPEEDES currently runs on UNIX networks and on the California Institute of Technology/Jet Propulsion Laboratory Mark III Hypercube. SPEEDES also supports interactive simulations. Featured in the SPEEDES environment is a new parallel synchronization approach called Breathing Time Buckets. This algorithm uses some of the conservative techniques found in Time Bucket synchronization, along with the optimism that characterizes the Time Warp approach. A mathematical model derived from first principles predicts the performance of Breathing Time Buckets. Along with the Breathing Time Buckets algorithm, this paper discusses the rules for processing events in SPEEDES, describes the implementation of various other synchronization protocols supported by SPEEDES, describes some new ones for the future, discusses interactive simulations, and then gives some performance results.

New type of chaos synchronization in discrete-time systems: the F-M synchronization

Directory of Open Access Journals (Sweden)

Ouannas Adel

2018-04-01

Full Text Available In this paper, a new type of synchronization for chaotic (hyperchaotic maps with different dimensions is proposed. The novel scheme is called F – M synchronization, since it combines the inverse generalized synchronization (based on a functional relationship F with the matrix projective synchronization (based on a matrix M. In particular, the proposed approach enables F – M synchronization with index d to be achieved between n-dimensional drive system map and m-dimensional response system map, where the synchronization index d corresponds to the dimension of the synchronization error. The technique, which exploits nonlinear controllers and Lyapunov stability theory, proves to be effective in achieving the F – M synchronization not only when the synchronization index d equals n or m, but even if the synchronization index d is larger than the map dimensions n and m. Finally, simulation results are reported, with the aim to illustrate the capabilities of the novel scheme proposed herein.

New type of chaos synchronization in discrete-time systems: the F-M synchronization

Science.gov (United States)

Ouannas, Adel; Grassi, Giuseppe; Karouma, Abdulrahman; Ziar, Toufik; Wang, Xiong; Pham, Viet-Thanh

2018-04-01

In this paper, a new type of synchronization for chaotic (hyperchaotic) maps with different dimensions is proposed. The novel scheme is called F - M synchronization, since it combines the inverse generalized synchronization (based on a functional relationship F) with the matrix projective synchronization (based on a matrix M). In particular, the proposed approach enables F - M synchronization with index d to be achieved between n-dimensional drive system map and m-dimensional response system map, where the synchronization index d corresponds to the dimension of the synchronization error. The technique, which exploits nonlinear controllers and Lyapunov stability theory, proves to be effective in achieving the F - M synchronization not only when the synchronization index d equals n or m, but even if the synchronization index d is larger than the map dimensions n and m. Finally, simulation results are reported, with the aim to illustrate the capabilities of the novel scheme proposed herein.

Nonoccurrence of Negotiation of Meaning in Task-Based Synchronous Computer-Mediated Communication

Science.gov (United States)

Van Der Zwaard, Rose; Bannink, Anne

2016-01-01

This empirical study investigated the occurrence of meaning negotiation in an interactive synchronous computer-mediated second language (L2) environment. Sixteen dyads (N = 32) consisting of nonnative speakers (NNSs) and native speakers (NSs) of English performed 2 different tasks using videoconferencing and written chat. The data were coded and…

Synchronous and Asynchronous Communication in Distance Learning: A Review of the Literature

Science.gov (United States)

Watts, Lynette

2016-01-01

Distance learning is commonplace in higher education, with increasing numbers of students enjoying the flexibility e-learning provides. Keeping students connected with peers and instructors has been a challenge with e-learning, but as technology has advanced, the methods by which educators keep students engaged, synchronously and asynchronously,…

Sensorimotor synchronization with different metrical levels of point-light dance movements

Directory of Open Access Journals (Sweden)

Yi-Huang eSu

2016-04-01

Full Text Available Rhythm perception and synchronization have been extensively investigated in the auditory domain, as they underlie means of human communication such as music and speech. Although recent studies suggest comparable mechanisms for synchronizing with periodically moving visual objects, the extent to which it applies to ecologically relevant information, such as the rhythm of complex biological motion, remains unknown. The present study addressed this issue by linking rhythm of music and dance in the framework of action-perception coupling. As a previous study showed that observers perceived multiple metrical periodicities in dance movements that embodied this structure, the present study examined whether sensorimotor synchronization (SMS to dance movements resembles what is known of auditory SMS. Participants watched a point-light figure performing two basic steps of Swing dance cyclically, in which the trunk bounced at every beat and the limbs moved at every second beat, forming two metrical periodicities. Participants tapped synchronously to the bounce of the trunk with or without the limbs moving in the stimuli (Experiment 1, or tapped synchronously to the leg movements with or without the trunk bouncing simultaneously (Experiment 2. Results showed that, while synchronization with the bounce (lower-level pulse was not influenced by the presence or absence of limb movements (metrical accent, synchronization with the legs (beat was improved by the presence of the bounce (metrical subdivision across different movement types. The latter finding parallels the subdivision benefit often demonstrated in auditory tasks, suggesting common sensorimotor mechanisms for visual rhythms in dance and auditory rhythms in music.

Sensorimotor Synchronization with Different Metrical Levels of Point-Light Dance Movements

Science.gov (United States)

Su, Yi-Huang

2016-01-01

Rhythm perception and synchronization have been extensively investigated in the auditory domain, as they underlie means of human communication such as music and speech. Although recent studies suggest comparable mechanisms for synchronizing with periodically moving visual objects, the extent to which it applies to ecologically relevant information, such as the rhythm of complex biological motion, remains unknown. The present study addressed this issue by linking rhythm of music and dance in the framework of action-perception coupling. As a previous study showed that observers perceived multiple metrical periodicities in dance movements that embodied this structure, the present study examined whether sensorimotor synchronization (SMS) to dance movements resembles what is known of auditory SMS. Participants watched a point-light figure performing two basic steps of Swing dance cyclically, in which the trunk bounced at every beat and the limbs moved at every second beat, forming two metrical periodicities. Participants tapped synchronously to the bounce of the trunk with or without the limbs moving in the stimuli (Experiment 1), or tapped synchronously to the leg movements with or without the trunk bouncing simultaneously (Experiment 2). Results showed that, while synchronization with the bounce (lower-level pulse) was not influenced by the presence or absence of limb movements (metrical accent), synchronization with the legs (beat) was improved by the presence of the bounce (metrical subdivision) across different movement types. The latter finding parallels the “subdivision benefit” often demonstrated in auditory tasks, suggesting common sensorimotor mechanisms for visual rhythms in dance and auditory rhythms in music. PMID:27199709

Iron Loss Prediction Using Modified IEM-Formula during the Field Weakening for Permanent Magnet Synchronous Machines

Directory of Open Access Journals (Sweden)

Pedram Asef

2017-12-01

Full Text Available During field weakening operation time (FWOT, the total iron loss rises and affects the accuracy of loss prediction and efficiency, especially if a large range of FWOT exists due to a large voltage drop that was rooted from the resistance of the used material. Iron loss prediction is widely employed in investigations for a fast electrical machine analysis using 2D finite element analysis (FEA. This paper proposes harmonic loss analytically by a steady-state equivalent circuit with a novel procedure. Consideration of skin effects and iron saturation are utilized in order to examine the accuracy through the relative error distribution in the frequency domain of each model from 50 to 700 Hz. Additionally, this comparative study presents a torque-frequency-field density calculation over each single term of the modified institute of electrical machines formula (IEM-Formula. The proposed analytical calculation is performed using 2D FEA for a classic and modified IEM-Formula along with experimental verifications on a surface-mounted permanent magnet synchronous generator (PMSG for a wind generation application.

[Cost-effectiveness of Synchronous vs. Asynchronous Telepsychiatry in Prison Inmates With Depression].

Science.gov (United States)

Barrera-Valencia, Camilo; Benito-Devia, Alexis Vladimir; Vélez-Álvarez, Consuelo; Figueroa-Barrera, Mario; Franco-Idárraga, Sandra Milena

Telepsychiatry is defined as the use of information and communication technology (ICT) in providing remote psychiatric services. Telepsychiatry is applied using two types of communication: synchronous (real time) and asynchronous (store and forward). To determine the cost-effectiveness of a synchronous and an asynchronous telepsychiatric model in prison inmate patients with symptoms of depression. A cost-effectiveness study was performed on a population consisting of 157 patients from the Establecimiento Penitenciario y Carcelario de Mediana Seguridad de Manizales, Colombia. The sample was determined by applying Zung self-administered surveys for depression (1965) and the Hamilton Depression Rating Scale (HDRS), the latter being the tool used for the comparison. Initial Hamilton score, arrival time, duration of system downtime, and clinical effectiveness variables had normal distributions (P>.05). There were significant differences (P<.001) between care costs for the different models, showing that the mean cost of the asynchronous model is less than synchronous model, and making the asynchronous model more cost-effective. The asynchronous model is the most cost-effective model of telepsychiatry care for patients with depression admitted to a detention centre, according to the results of clinical effectiveness, cost measurement, and patient satisfaction. Copyright © 2016 Asociación Colombiana de Psiquiatría. Publicado por Elsevier España. All rights reserved.

Synchronous spikes are necessary but not sufficient for a synchrony code in populations of spiking neurons.

Science.gov (United States)

Grewe, Jan; Kruscha, Alexandra; Lindner, Benjamin; Benda, Jan

2017-03-07

Synchronous activity in populations of neurons potentially encodes special stimulus features. Selective readout of either synchronous or asynchronous activity allows formation of two streams of information processing. Theoretical work predicts that such a synchrony code is a fundamental feature of populations of spiking neurons if they operate in specific noise and stimulus regimes. Here we experimentally test the theoretical predictions by quantifying and comparing neuronal response properties in tuberous and ampullary electroreceptor afferents of the weakly electric fish Apteronotus leptorhynchus These related systems show similar levels of synchronous activity, but only in the more irregularly firing tuberous afferents a synchrony code is established, whereas in the more regularly firing ampullary afferents it is not. The mere existence of synchronous activity is thus not sufficient for a synchrony code. Single-cell features such as the irregularity of spiking and the frequency dependence of the neuron's transfer function determine whether synchronous spikes possess a distinct meaning for the encoding of time-dependent signals.

Timing subsystem development: Network synchronization experiments

Science.gov (United States)

Backe, K. R.

1983-01-01

This paper describes a program in which several experimental timing subsystem prototypes were designed, fabricated, and field tested using a small network of troposcatter and microwave digital communication links. This equipment was responsible for modem/radio interfacing, time interval measurement, clock adjustment and distribution, synchronization technique, and node to node information exchange. Presented are discussions of the design approach, measurement plan, and performance assessment methods. Recommendations are made based on the findings of the test program and an evaluation of the design of both the hardware and software elements of the timing subsystem prototypes.

Stages of chaotic synchronization.

Science.gov (United States)

Tang, D. Y.; Dykstra, R.; Hamilton, M. W.; Heckenberg, N. R.

1998-09-01

In an experimental investigation of the response of a chaotic system to a chaotic driving force, we have observed synchronization of chaos of the response system in the forms of generalized synchronization, phase synchronization, and lag synchronization to the driving signal. In this paper we compare the features of these forms of synchronized chaos and study their relations and physical origins. We found that different forms of chaotic synchronization could be interpreted as different stages of nonlinear interaction between the coupled chaotic systems. (c) 1998 American Institute of Physics.

Synchronous ethernet and IEEE 1588 in telecoms next generation synchronization networks

CERN Document Server

2013-01-01

This book addresses the multiple technical aspects of the distribution of synchronization in new generation telecommunication networks, focusing in particular on synchronous Ethernet and IEEE1588 technologies. Many packet network engineers struggle with understanding the challenges that precise synchronization distribution can impose on networks. The usual “why”, “when” and particularly “how” can cause problems for many engineers. In parallel to this, some other markets have identical synchronization requirements, but with their own design requirements, generating further questions. This book attempts to respond to the different questions by providing background technical information. Invaluable information on state of-the-art packet network synchronization and timing architectures is provided, as well as an unbiased view on the synchronization technologies that have been internationally standardized over recent years, with the aim of providing the average reader (who is not skilled in the art) wi...

On the anti-synchronization detection for the generalized Lorenz system and its applications to secure encryption

Czech Academy of Sciences Publication Activity Database

Lynnyk, Volodymyr; Čelikovský, Sergej

2010-01-01

Roč. 46, č. 1 (2010), s. 1-18 ISSN 0023-5954 R&D Projects: GA ČR(CZ) GA102/08/0186 Institutional research plan: CEZ:AV0Z10750506 Keywords : observer * nonlinear system * chaos shift keying * generalized Lorenz system * synchronization * anti-synchronization * secure communication Subject RIV: BC - Control Systems Theory Impact factor: 0.461, year: 2010 http://library.utia.cas.cz/separaty/2010/TR/lynnyk-0342105.pdf

Predicting functional communication ability in children with cerebral palsy at school entry.

Science.gov (United States)

Coleman, Andrea; Weir, Kelly; Ware, Robert S; Boyd, Roslyn

2015-03-01

To explore the value of demographic, environmental, and early clinical characteristics in predicting functional communication in children with cerebral palsy (CP) at school entry. Data are from an Australian prospective longitudinal study of children with CP. Children assessed at 18 to 24 and 48 to 60 months corrected age were included in the study. Functional communication was classified at 48 to 60 months using the Communication Function Classification System (CFCS). Predictive variables included communication skills at 18 to 24 months, evaluated using the Communication and Symbolic Behavioural Scales Developmental Profile (CSBS-DP) Infant-Toddler Checklist. Early Gross Motor Function Classification System (GMFCS), Manual Ability Classification System, and motor type and distribution were evaluated by two physiotherapists. Demographic and comorbid variables were obtained through parent interview with a paediatrician or rehabilitation specialist. A total of 114 children (76 males, 38 females) were included in the study. At 18 to 24 months the mean CSBS-DP was 84.9 (SD 19.0). The CFCS distribution at 48 to 60 months was I=36(32%), II=25(22%), III=20(18%), IV=19(17%), and V=14(12%). In multivariable regression analysis, only CSBS-DP (pcommunication at school entry. Body structure and function and not environmental factors impact functional communication at school entry in children with CP. This provides valuable guidance for early screening, parent education, and future planning of intervention programs to improve functional communication. © 2014 Mac Keith Press.

Impulsive Synchronization and Adaptive-Impulsive Synchronization of a Novel Financial Hyperchaotic System

Directory of Open Access Journals (Sweden)

Xiuli Chai

2013-01-01

Full Text Available The impulsive synchronization and adaptive-impulsive synchronization of a novel financial hyperchaotic system are investigated. Based on comparing principle for impulsive functional differential equations, several sufficient conditions for impulsive synchronization are derived, and the upper bounds of impulsive interval for stable synchronization are estimated. Furthermore, a nonlinear adaptive-impulsive control scheme is designed to synchronize the financial system using invariant principle of impulsive dynamical systems. Moreover, corresponding numerical simulations are presented to illustrate the effectiveness and feasibility of the proposed methods.

Synchronization of stochastic delayed neural networks with markovian switching and its application.

Science.gov (United States)

Tang, Yang; Fang, Jian-An; Miao, Qing-Ying

2009-02-01

In this paper, the problem of adaptive synchronization for a class of stochastic neural networks (SNNs) which involve both mixed delays and Markovian jumping parameters is investigated. The mixed delays comprise the time-varying delays and distributed delays, both of which are mode-dependent. The stochastic perturbations are described in terms of Browian motion. By the adaptive feedback technique, several sufficient criteria have been proposed to ensure the synchronization of SNNs in mean square. Moreover, the proposed adaptive feedback scheme is applied to the secure communication. Finally, the corresponding simulation results are given to demonstrate the usefulness of the main results obtained.

An Empirical Investigation of Student Acceptance of Synchronous E-Learning in an Online University

Science.gov (United States)

Kang, Minseok; Shin, Won sug

2015-01-01

This study proposes an extended technology acceptance model to predict acceptance of synchronous e-learning by examining relationships among variables associated with factors influencing the technology acceptance of synchronous e-learning. Learners at an online university participated through an online survey; there were 251 respondents in all.…

Analytical study of synchronization in spin-transfer-driven magnetization dynamics

Energy Technology Data Exchange (ETDEWEB)

Bonin, Roberto [Politecnico di Torino - sede di Verres, via Luigi Barone 8, I-11029 Verres (Italy); Bertotti, Giorgio; Bortolotti, Paolo [Istituto Nazionale di Ricerca Metrologica, Strada delle Cacce 91, I-10135 Torino (Italy); Serpico, Claudio [Dipartimento di Ingegneria Elettrica, Universita di Napoli ' Federico II' , via Claudio 21, I-80125 Napoli (Italy); D' Aquino, Massimiliano [Dipartimento per le Tecnologie, Universita di Napoli ' Parthenope' , via Medina 40, I-80133 Napoli (Italy); Mayergoyz, Isaak D, E-mail: p.bortolotti@inrim.i [Electrical and Computer Engineering Department and UMIACS, University of Maryland, College Park MD 20742 (United States)

2010-01-01

An analytical study of the synchronization effects in spin-transfer-driven nanomagnets subjected to either microwave magnetic fields or microwave electrical currents is discussed. Appropriate stability diagrams are constructed and the conditions under which the current-induced magnetization precession is synchronized by the microwave external excitation are derived and discussed. Analytical predictions are given for the existence of phase-locking effects in current-induced magnetization precessions and for the occurrence of hysteresis in phase-locking as a function of the spin-polarized current.

Phase synchronization of instrumental music signals

Science.gov (United States)

Mukherjee, Sayan; Palit, Sanjay Kumar; Banerjee, Santo; Ariffin, M. R. K.; Bhattacharya, D. K.

2014-06-01

Signal analysis is one of the finest scientific techniques in communication theory. Some quantitative and qualitative measures describe the pattern of a music signal, vary from one to another. Same musical recital, when played by different instrumentalists, generates different types of music patterns. The reason behind various patterns is the psycho-acoustic measures - Dynamics, Timber, Tonality and Rhythm, varies in each time. However, the psycho-acoustic study of the music signals does not reveal any idea about the similarity between the signals. For such cases, study of synchronization of long-term nonlinear dynamics may provide effective results. In this context, phase synchronization (PS) is one of the measures to show synchronization between two non-identical signals. In fact, it is very critical to investigate any other kind of synchronization for experimental condition, because those are completely non identical signals. Also, there exists equivalence between the phases and the distances of the diagonal line in Recurrence plot (RP) of the signals, which is quantifiable by the recurrence quantification measure τ-recurrence rate. This paper considers two nonlinear music signals based on same raga played by two eminent sitar instrumentalists as two non-identical sources. The psycho-acoustic study shows how the Dynamics, Timber, Tonality and Rhythm vary for the two music signals. Then, long term analysis in the form of phase space reconstruction is performed, which reveals the chaotic phase spaces for both the signals. From the RP of both the phase spaces, τ-recurrence rate is calculated. Finally by the correlation of normalized tau-recurrence rate of their 3D phase spaces and the PS of the two music signals has been established. The numerical results well support the analysis.

Health Communication in Social Media: Message Features Predicting User Engagement on Diabetes-Related Facebook Pages.

Science.gov (United States)

Rus, Holly M; Cameron, Linda D

2016-10-01

Social media provides unprecedented opportunities for enhancing health communication and health care, including self-management of chronic conditions such as diabetes. Creating messages that engage users is critical for enhancing message impact and dissemination. This study analyzed health communications within ten diabetes-related Facebook pages to identify message features predictive of user engagement. The Common-Sense Model of Illness Self-Regulation and established health communication techniques guided content analyses of 500 Facebook posts. Each post was coded for message features predicted to engage users and numbers of likes, shares, and comments during the week following posting. Multi-level, negative binomial regressions revealed that specific features predicted different forms of engagement. Imagery emerged as a strong predictor; messages with images had higher rates of liking and sharing relative to messages without images. Diabetes consequence information and positive identity predicted higher sharing while negative affect, social support, and crowdsourcing predicted higher commenting. Negative affect, crowdsourcing, and use of external links predicted lower sharing while positive identity predicted lower commenting. The presence of imagery weakened or reversed the positive relationships of several message features with engagement. Diabetes control information and negative affect predicted more likes in text-only messages, but fewer likes when these messages included illustrative imagery. Similar patterns of imagery's attenuating effects emerged for the positive relationships of consequence information, control information, and positive identity with shares and for positive relationships of negative affect and social support with comments. These findings hold promise for guiding communication design in health-related social media.

The accuracy with which adults who do not stutter predict stuttering-related communication attitudes.

Science.gov (United States)

Logan, Kenneth J; Willis, Julie R

2011-12-01

The purpose of this study was to examine the extent to which adults who do not stutter can predict communication-related attitudes of adults who do stutter. 40 participants (mean age of 22.5 years) evaluated speech samples from an adult with mild stuttering and an adult with severe stuttering via audio-only (n=20) or audio-visual (n=20) modes to predict how the adults had responded on the S24 scale of communication attitudes. Participants correctly predicted which speaker had the more favorable S24 score, and the predicted scores were significantly different between the severity conditions. Across the four subgroups, predicted S24 scores differed from actual scores by 4-9 points. Predicted values were greater than the actual values for 3 of 4 subgroups, but still relatively positive in relation to the S24 norm sample. Stimulus presentation mode interacted with stuttering severity to affect prediction accuracy. The participants predicted the speakers' negative self-attributions more accurately than their positive self-attributions. Findings suggest that adults who do not stutter estimate the communication-related attitudes of specific adults who stutter in a manner that is generally accurate, though, in some conditions, somewhat less favorable than the speaker's actual ratings. At a group level, adults who do not stutter demonstrate the ability to discern minimal versus average levels of attitudinal impact for speakers who stutter. The participants' complex prediction patterns are discussed in relation to stereotype accuracy and classic views of negative stereotyping. The reader will be able to (a) summarize main findings on research related to listeners' attitudes toward people who stutter, (b) describe the extent to which people who do not stutter can predict the communication attitudes of people who do stutter; and (c) discuss how findings from the present study relate to previous findings on stereotypes about people who stutter. Copyright © 2011 Elsevier Inc

Pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions

International Nuclear Information System (INIS)

Yan-Li, Zou; Guan-Rong, Chen

2009-01-01

This paper studies pinning-controlled synchronization of complex networks with bounded or unbounded synchronized regions. To study a state-feedback pinning-controlled network with N nodes, it first converts the controlled network to an extended network of N+1 nodes without controls. It is shown that the controlled synchronizability of the given network is determined by the real part of the smallest nonzero eigenvalue of the coupling matrix of its extended network when the synchronized region is unbounded; but it is determined by the ratio of the real parts of the largest and the smallest nonzero eigenvalues of the coupling matrix when the synchronized region is bounded. Both theoretical analysis and numerical simulation show that the portion of controlled nodes has no critical values when the synchronized region is unbounded, but it has a critical value when the synchronized region is bounded. In the former case, therefore, it is possible to control the network to achieve synchronization by pinning only one node. In the latter case, the network can achieve controlled synchronization only when the portion of controlled nodes is larger than the critical value. (general)

Communicating Mathematics on the Internet: Synchronous and Asynchronous Tools

Science.gov (United States)

Hodges, Charles B.; Hunger, Gail M.

2011-01-01

Communicating and collaborating online are becoming common requirements in education. The specialized notations and symbols necessary for some content areas where mathematical expressions are part of the conversation require that users select appropriate communication tools. The purpose of this article is to describe tools that can be used for…

Subthalamic stimulation modulates cortical motor network activity and synchronization in Parkinson’s disease

Science.gov (United States)

Klotz, Rosa; Govindan, Rathinaswamy B.; Scholten, Marlieke; Naros, Georgios; Ramos-Murguialday, Ander; Bunjes, Friedemann; Meisner, Christoph; Plewnia, Christian; Krüger, Rejko

2015-01-01

Dynamic modulations of large-scale network activity and synchronization are inherent to a broad spectrum of cognitive processes and are disturbed in neuropsychiatric conditions including Parkinson’s disease. Here, we set out to address the motor network activity and synchronization in Parkinson’s disease and its modulation with subthalamic stimulation. To this end, 20 patients with idiopathic Parkinson’s disease with subthalamic nucleus stimulation were analysed on externally cued right hand finger movements with 1.5-s interstimulus interval. Simultaneous recordings were obtained from electromyography on antagonistic muscles (right flexor digitorum and extensor digitorum) together with 64-channel electroencephalography. Time-frequency event-related spectral perturbations were assessed to determine cortical and muscular activity. Next, cross-spectra in the time-frequency domain were analysed to explore the cortico-cortical synchronization. The time-frequency modulations enabled us to select a time-frequency range relevant for motor processing. On these time-frequency windows, we developed an extension of the phase synchronization index to quantify the global cortico-cortical synchronization and to obtain topographic differentiations of distinct electrode sites with respect to their contributions to the global phase synchronization index. The spectral measures were used to predict clinical and reaction time outcome using regression analysis. We found that movement-related desynchronization of cortical activity in the upper alpha and beta range was significantly facilitated with ‘stimulation on’ compared to ‘stimulation off’ on electrodes over the bilateral parietal, sensorimotor, premotor, supplementary-motor, and prefrontal areas, including the bilateral inferior prefrontal areas. These spectral modulations enabled us to predict both clinical and reaction time improvement from subthalamic stimulation. With ‘stimulation on’, interhemispheric cortico

Adaptive control of dynamical synchronization on evolving networks with noise disturbances

Science.gov (United States)

Yuan, Wu-Jie; Zhou, Jian-Fang; Sendiña-Nadal, Irene; Boccaletti, Stefano; Wang, Zhen

2018-02-01

In real-world networked systems, the underlying structure is often affected by external and internal unforeseen factors, making its evolution typically inaccessible. An adaptive strategy was introduced for maintaining synchronization on unpredictably evolving networks [Sorrentino and Ott, Phys. Rev. Lett. 100, 114101 (2008), 10.1103/PhysRevLett.100.114101], which yet does not consider the noise disturbances widely existing in networks' environments. We provide here strategies to control dynamical synchronization on slowly and unpredictably evolving networks subjected to noise disturbances which are observed at the node and at the communication channel level. With our strategy, the nodes' coupling strength is adaptively adjusted with the aim of controlling synchronization, and according only to their received signal and noise disturbances. We first provide a theoretical analysis of the control scheme by introducing an error potential function to seek for the minimization of the synchronization error. Then, we show numerical experiments which verify our theoretical results. In particular, it is found that our adaptive strategy is effective even for the case in which the dynamics of the uncontrolled network would be explosive (i.e., the states of all the nodes would diverge to infinity).

Patient-provider communication and low-income adults: age, race, literacy, and optimism predict communication satisfaction.

Science.gov (United States)

Jensen, Jakob D; King, Andy J; Guntzviller, Lisa M; Davis, LaShara A

2010-04-01

To assess whether literacy, numeracy, and optimism are related to low-income adults' satisfaction with their healthcare provider's communication skills. Low-income adults (N=131) were recruited from seven counties in Indiana through University extension programs. To achieve research triangulation, participants were surveyed and interviewed about their communication satisfaction with health providers. Survey data revealed that four variables significantly predicted satisfaction: age, race, literacy, and optimism. Low-income adults in the current study were more critical of their healthcare provider's communication skills if they were younger, White, functionally literate, and pessimistic. Follow-up interviews confirmed this pattern and suggested it was a byproduct of patient activism. In low-income populations, communication satisfaction may be lower for groups that are traditionally active in doctor-patient interactions (e.g., younger patients, patients with higher literacy skills). Healthcare providers should be aware that older, non-White, optimistic, and literacy deficient patients report greater communication satisfaction than their younger, White, pessimistic, and functionally literate peers. Both groups may be coping with their situation, the former by withdrawing and the latter by actively pushing for a higher standard of care. Healthcare providers should continue to seek out ways to facilitate dialogue with these underserved groups. 2009 Elsevier Ireland Ltd. All rights reserved.

Who benefits from synchronous online communication?: A comparison of face-to-face and synchronous online interviews with children

OpenAIRE

Enochsson, Ann-Britt

2011-01-01

This paper is based on experiences from three different research projects in which both face-to-face (f2f) and synchronous online (IM) interviews were used, and it discusses what different media can mean to different respondents. The interviewees were between 10 and 16 years old. The analyses were made from transcripts of 25 f2f interviews and 23 IM interviews. The flow of the dialogue and the amount of words used has been analysed. The answers were longer in f2f interviews, but in f2f interv...

Bluetooth Based Chaos Synchronization Using Particle Swarm Optimization and Its Applications to Image Encryption

Directory of Open Access Journals (Sweden)

Tzu-Hsiang Hung

2012-06-01

Full Text Available This study used the complex dynamic characteristics of chaotic systems and Bluetooth to explore the topic of wireless chaotic communication secrecy and develop a communication security system. The PID controller for chaos synchronization control was applied, and the optimum parameters of this PID controller were obtained using a Particle Swarm Optimization (PSO algorithm. Bluetooth was used to realize wireless transmissions, and a chaotic wireless communication security system was developed in the design concept of a chaotic communication security system. The experimental results show that this scheme can be used successfully in image encryption.

Optical Communications Channel Combiner

Science.gov (United States)

Quirk, Kevin J.; Quirk, Kevin J.; Nguyen, Danh H.; Nguyen, Huy

2012-01-01

NASA has identified deep-space optical communications links as an integral part of a unified space communication network in order to provide data rates in excess of 100 Mb/s. The distances and limited power inherent in a deep-space optical downlink necessitate the use of photon-counting detectors and a power-efficient modulation such as pulse position modulation (PPM). For the output of each photodetector, whether from a separate telescope or a portion of the detection area, a communication receiver estimates a log-likelihood ratio for each PPM slot. To realize the full effective aperture of these receivers, their outputs must be combined prior to information decoding. A channel combiner was developed to synchronize the log-likelihood ratio (LLR) sequences of multiple receivers, and then combines these into a single LLR sequence for information decoding. The channel combiner synchronizes the LLR sequences of up to three receivers and then combines these into a single LLR sequence for output. The channel combiner has three channel inputs, each of which takes as input a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The cross-correlation between the channels LLR time series are calculated and used to synchronize the sequences prior to combining. The output of the channel combiner is a sequence of four-bit LLRs for each PPM slot in a codeword via a XAUI 10 Gb/s quad optical fiber interface. The unit is controlled through a 1 Gb/s Ethernet UDP/IP interface. A deep-space optical communication link has not yet been demonstrated. This ground-station channel combiner was developed to demonstrate this capability and is unique in its ability to process such a signal.

Generalized synchronization-based multiparameter estimation in modulated time-delayed systems

Science.gov (United States)

Ghosh, Dibakar; Bhattacharyya, Bidyut K.

2011-09-01

We propose a nonlinear active observer based generalized synchronization scheme for multiparameter estimation in time-delayed systems with periodic time delay. A sufficient condition for parameter estimation is derived using Krasovskii-Lyapunov theory. The suggested tool proves to be globally and asymptotically stable by means of Krasovskii-Lyapunov method. With this effective method, parameter identification and generalized synchronization of modulated time-delayed systems with all the system parameters unknown, can be achieved simultaneously. We restrict our study for multiple parameter estimation in modulated time-delayed systems with single state variable only. Theoretical proof and numerical simulation demonstrate the effectiveness and feasibility of the proposed technique. The block diagram of electronic circuit for multiple time delay system shows that the method is easily applicable in practical communication problems.

Synchronization on effective networks

International Nuclear Information System (INIS)

Zhou Tao; Zhao Ming; Zhou Changsong

2010-01-01

The study of network synchronization has attracted increasing attentionrecently. In this paper, we strictly define a class of networks, namely effective networks, which are synchronizable and orientable networks. We can prove that all the effective networks with the same size have the same spectra, and are of the best synchronizability according to the master stability analysis. However, it is found that the synchronization time for different effective networks can be quite different. Further analysis shows that the key ingredient affecting the synchronization time is the maximal depth of an effective network: the larger depth results in a longer synchronization time. The secondary factor is the number of links. The increasing number of links connecting nodes in the same layer (horizontal links) will lead to longer synchronization time, whereas the increasing number of links connecting nodes in neighboring layers (vertical links) will accelerate the synchronization. Our analysis of the relationship between the structure and synchronization properties of the original and effective networks shows that the purely directed effective network can provide an approximation of the original weighted network with normalized input strength. Our findings provide insights into the roles of depth, horizontal and vertical links in the synchronizing process, and suggest that the spectral analysis is helpful yet insufficient for the comprehensive understanding of network synchronization.

Synchronization on effective networks

Energy Technology Data Exchange (ETDEWEB)

Zhou Tao [Web Sciences Center, University of Electronic Science and Technology of China, Chengdu 610054 (China); Zhao Ming [Department of Modern Physics, University of Science and Technology of China, Hefei 230026 (China); Zhou Changsong, E-mail: cszhou@hkbu.edu.h [Department of Physics, Hong Kong Baptist University, Kowloon Tong (Hong Kong)

2010-04-15

The study of network synchronization has attracted increasing attentionrecently. In this paper, we strictly define a class of networks, namely effective networks, which are synchronizable and orientable networks. We can prove that all the effective networks with the same size have the same spectra, and are of the best synchronizability according to the master stability analysis. However, it is found that the synchronization time for different effective networks can be quite different. Further analysis shows that the key ingredient affecting the synchronization time is the maximal depth of an effective network: the larger depth results in a longer synchronization time. The secondary factor is the number of links. The increasing number of links connecting nodes in the same layer (horizontal links) will lead to longer synchronization time, whereas the increasing number of links connecting nodes in neighboring layers (vertical links) will accelerate the synchronization. Our analysis of the relationship between the structure and synchronization properties of the original and effective networks shows that the purely directed effective network can provide an approximation of the original weighted network with normalized input strength. Our findings provide insights into the roles of depth, horizontal and vertical links in the synchronizing process, and suggest that the spectral analysis is helpful yet insufficient for the comprehensive understanding of network synchronization.

GABA and Gap Junctions in the Development of Synchronized Activity in Human Pluripotent Stem Cell-Derived Neural Networks

Directory of Open Access Journals (Sweden)

Meeri Eeva-Liisa Mäkinen

2018-03-01

Full Text Available The electrical activity of the brain arises from single neurons communicating with each other. However, how single neurons interact during early development to give rise to neural network activity remains poorly understood. We studied the emergence of synchronous neural activity in human pluripotent stem cell (hPSC-derived neural networks simultaneously on a single-neuron level and network level. The contribution of gamma-aminobutyric acid (GABA and gap junctions to the development of synchronous activity in hPSC-derived neural networks was studied with GABA agonist and antagonist and by blocking gap junctional communication, respectively. We characterized the dynamics of the network-wide synchrony in hPSC-derived neural networks with high spatial resolution (calcium imaging and temporal resolution microelectrode array (MEA. We found that the emergence of synchrony correlates with a decrease in very strong GABA excitation. However, the synchronous network was found to consist of a heterogeneous mixture of synchronously active cells with variable responses to GABA, GABA agonists and gap junction blockers. Furthermore, we show how single-cell distributions give rise to the network effect of GABA, GABA agonists and gap junction blockers. Finally, based on our observations, we suggest that the earliest form of synchronous neuronal activity depends on gap junctions and a decrease in GABA induced depolarization but not on GABAA mediated signaling.

GABA and Gap Junctions in the Development of Synchronized Activity in Human Pluripotent Stem Cell-Derived Neural Networks

Science.gov (United States)

Mäkinen, Meeri Eeva-Liisa; Ylä-Outinen, Laura; Narkilahti, Susanna

2018-01-01

The electrical activity of the brain arises from single neurons communicating with each other. However, how single neurons interact during early development to give rise to neural network activity remains poorly understood. We studied the emergence of synchronous neural activity in human pluripotent stem cell (hPSC)-derived neural networks simultaneously on a single-neuron level and network level. The contribution of gamma-aminobutyric acid (GABA) and gap junctions to the development of synchronous activity in hPSC-derived neural networks was studied with GABA agonist and antagonist and by blocking gap junctional communication, respectively. We characterized the dynamics of the network-wide synchrony in hPSC-derived neural networks with high spatial resolution (calcium imaging) and temporal resolution microelectrode array (MEA). We found that the emergence of synchrony correlates with a decrease in very strong GABA excitation. However, the synchronous network was found to consist of a heterogeneous mixture of synchronously active cells with variable responses to GABA, GABA agonists and gap junction blockers. Furthermore, we show how single-cell distributions give rise to the network effect of GABA, GABA agonists and gap junction blockers. Finally, based on our observations, we suggest that the earliest form of synchronous neuronal activity depends on gap junctions and a decrease in GABA induced depolarization but not on GABAA mediated signaling. PMID:29559893

Thermal and orbital analysis of Earth monitoring Sun-synchronous space experiments

Science.gov (United States)

Killough, Brian D.

1990-01-01

The fundamentals of an Earth monitoring Sun-synchronous orbit are presented. A Sun-synchronous Orbit Analysis Program (SOAP) was developed to calculate orbital parameters for an entire year. The output from this program provides the required input data for the TRASYS thermal radiation computer code, which in turn computes the infrared, solar and Earth albedo heat fluxes incident on a space experiment. Direct incident heat fluxes can be used as input to a generalized thermal analyzer program to size radiators and predict instrument operating temperatures. The SOAP computer code and its application to the thermal analysis methodology presented, should prove useful to the thermal engineer during the design phases of Earth monitoring Sun-synchronous space experiments.

The ADaptation and Anticipation Model (ADAM) of sensorimotor synchronization

Science.gov (United States)

van der Steen, M. C. (Marieke); Keller, Peter E.

2013-01-01

A constantly changing environment requires precise yet flexible timing of movements. Sensorimotor synchronization (SMS)—the temporal coordination of an action with events in a predictable external rhythm—is a fundamental human skill that contributes to optimal sensory-motor control in daily life. A large body of research related to SMS has focused on adaptive error correction mechanisms that support the synchronization of periodic movements (e.g., finger taps) with events in regular pacing sequences. The results of recent studies additionally highlight the importance of anticipatory mechanisms that support temporal prediction in the context of SMS with sequences that contain tempo changes. To investigate the role of adaptation and anticipatory mechanisms in SMS we introduce ADAM: an ADaptation and Anticipation Model. ADAM combines reactive error correction processes (adaptation) with predictive temporal extrapolation processes (anticipation) inspired by the computational neuroscience concept of internal models. The combination of simulations and experimental manipulations based on ADAM creates a novel and promising approach for exploring adaptation and anticipation in SMS. The current paper describes the conceptual basis and architecture of ADAM. PMID:23772211

Teacher Education: Modes of Communication within Asynchronous and Synchronous Communication Platforms

Science.gov (United States)

Madden, Lauren; Jones, Gail; Childers, Gina

2017-01-01

New tools for teaching with distance education afford students with a variety of modes of communication. This study examined students' interactions during an online science education course. All interactions that took place with Elluminate Chat, Elluminate Voice, and Moodle learning platforms were recorded, transcribed, and analyzed. Interactions…

Chaos Synchronization Based on Unknown Input Proportional Multiple-Integral Fuzzy Observer

Directory of Open Access Journals (Sweden)

T. Youssef

2013-01-01

Full Text Available This paper presents an unknown input Proportional Multiple-Integral Observer (PIO for synchronization of chaotic systems based on Takagi-Sugeno (TS fuzzy chaotic models subject to unmeasurable decision variables and unknown input. In a secure communication configuration, this unknown input is regarded as a message encoded in the chaotic system and recovered by the proposed PIO. Both states and outputs of the fuzzy chaotic models are subject to polynomial unknown input with kth derivative zero. Using Lyapunov stability theory, sufficient design conditions for synchronization are proposed. The PIO gains matrices are obtained by resolving linear matrix inequalities (LMIs constraints. Simulation results show through two TS fuzzy chaotic models the validity of the proposed method.

Synchronization of chaotic systems

International Nuclear Information System (INIS)

Pecora, Louis M.; Carroll, Thomas L.

2015-01-01

We review some of the history and early work in the area of synchronization in chaotic systems. We start with our own discovery of the phenomenon, but go on to establish the historical timeline of this topic back to the earliest known paper. The topic of synchronization of chaotic systems has always been intriguing, since chaotic systems are known to resist synchronization because of their positive Lyapunov exponents. The convergence of the two systems to identical trajectories is a surprise. We show how people originally thought about this process and how the concept of synchronization changed over the years to a more geometric view using synchronization manifolds. We also show that building synchronizing systems leads naturally to engineering more complex systems whose constituents are chaotic, but which can be tuned to output various chaotic signals. We finally end up at a topic that is still in very active exploration today and that is synchronization of dynamical systems in networks of oscillators

Feedback control and adaptive synchronization of chaotic forced Bonhoeffer-van der Pol oscillators

Energy Technology Data Exchange (ETDEWEB)

Kontchou, E W Chimi; Fotsin, H B [Laboratoire d' Electronique, Departement de Physique, Faculte des Sciences, Universite de Dschang, B P 67 Dschang (Cameroon); Woafo, P [Laboratory of Modelling and Simulation in Engineering and Biological Physics, Faculty of Science, University of Yaounde I, Box 812, Yaounde (Cameroon)], E-mail: hbfotsin@yahoo.fr

2008-04-15

This paper deals with chaos control and synchronization in forced Bonhoeffer-van der Pol (FBVP) oscillators. The state equations of the model are first established and the stability is analysed. A feedback control strategy for stabilizing the chaotic dynamics on a periodic orbit of the phase space is investigated. Adaptive synchronization of two FBVP oscillators, based on parameter estimation and a nonlinear observer approach, is also investigated. It appears that a particular unknown parameter of the model can be estimated, which gives the possibility of recovering information through chaotic masking. An application in secure communications is presented.

Feedback control and adaptive synchronization of chaotic forced Bonhoeffer-van der Pol oscillators

International Nuclear Information System (INIS)

Kontchou, E W Chimi; Fotsin, H B; Woafo, P

2008-01-01

This paper deals with chaos control and synchronization in forced Bonhoeffer-van der Pol (FBVP) oscillators. The state equations of the model are first established and the stability is analysed. A feedback control strategy for stabilizing the chaotic dynamics on a periodic orbit of the phase space is investigated. Adaptive synchronization of two FBVP oscillators, based on parameter estimation and a nonlinear observer approach, is also investigated. It appears that a particular unknown parameter of the model can be estimated, which gives the possibility of recovering information through chaotic masking. An application in secure communications is presented

Breaking chaotic shift key communication via adaptive key identification

International Nuclear Information System (INIS)

Ren Haipeng; Han Chongzhao; Liu Ding

2008-01-01

This paper proposes an adaptive parameter identification method for breaking chaotic shift key communication from the transmitted signal in public channel. The sensitive dependence property of chaos on parameter mismatch is used for chaos adaptive synchronization and parameter identification. An index function about the synchronization error is defined and conjugate gradient method is used to minimize the index function and to search the transmitter's parameter (key). By using proposed method, secure key is recovered from transmitted signal generated by low dimensional chaos and hyper chaos switching communication. Multi-parameters can also be identified from the transmitted signal with noise

Analysis of synchronous digital-modulation schemes for satellite communication

Science.gov (United States)

Takhar, G. S.; Gupta, S. C.

1975-01-01

The multipath communication channel for space communications is modeled as a multiplicative channel. This paper discusses the effects of multiplicative channel processes on the symbol error rate for quadrature modulation (QM) digital modulation schemes. An expression for the upper bound on the probability of error is derived and numerically evaluated. The results are compared with those obtained for additive channels.

Bus Based Synchronization Method for CHIPPER Based NoC

Directory of Open Access Journals (Sweden)

D. Muralidharan

2016-01-01

Full Text Available Network on Chip (NoC reduces the communication delay of System on Chip (SoC. The main limitation of NoC is power consumption and area overhead. Bufferless NoC reduces the area complexity and power consumption by eliminating buffers in the traditional routers. The bufferless NoC design should include live lock freeness since they use hot potato routing. This increases the complexity of bufferless NoC design. Among the available propositions to reduce this complexity, CHIPPER based bufferless NoC is considered as one of the best options. Live lock freeness is provided in CHIPPER through golden epoch and golden packet. All routers follow some synchronization method to identify a golden packet. Clock based method is intuitively followed for synchronization in CHIPPER based NoCs. It is shown in this work that the worst-case latency of packets is unbearably high when the above synchronization is followed. To alleviate this problem, broadcast bus NoC (BBus NoC approach is proposed in this work. The proposed method decreases the worst-case latency of packets by increasing the golden epoch rate of CHIPPER.

Chaos synchronization in vertical-cavity surface-emitting laser based on rotated polarization-preserved optical feedback.

Science.gov (United States)

Nazhan, Salam; Ghassemlooy, Zabih; Busawon, Krishna

2016-01-01

In this paper, the influence of the rotating polarization-preserved optical feedback on the chaos synchronization of a vertical-cavity surface-emitting laser (VCSEL) is investigated experimentally. Two VCSELs' polarization modes (XP) and (YP) are gradually rotated and re-injected back into the VCSEL. The anti-phase dynamics synchronization of the two polarization modes is evaluated using the cross-correlation function. For a fixed optical feedback, a clear relationship is found between the cross-correlation coefficient and the polarization angle θp. It is shown that high-quality anti-phase polarization-resolved chaos synchronization is achieved at higher values of θp. The maximum value of the cross-correlation coefficient achieved is -0.99 with a zero time delay over a wide range of θp beyond 65° with a poor synchronization dynamic at θp less than 65°. Furthermore, it is observed that the antiphase irregular oscillation of the XP and YP modes changes with θp. VCSEL under the rotating polarization optical feedback can be a good candidate as a chaotic synchronization source for a secure communication system.

Synchronized dynamic dose reconstruction

International Nuclear Information System (INIS)

Litzenberg, Dale W.; Hadley, Scott W.; Tyagi, Neelam; Balter, James M.; Ten Haken, Randall K.; Chetty, Indrin J.

2007-01-01

Variations in target volume position between and during treatment fractions can lead to measurable differences in the dose distribution delivered to each patient. Current methods to estimate the ongoing cumulative delivered dose distribution make idealized assumptions about individual patient motion based on average motions observed in a population of patients. In the delivery of intensity modulated radiation therapy (IMRT) with a multi-leaf collimator (MLC), errors are introduced in both the implementation and delivery processes. In addition, target motion and MLC motion can lead to dosimetric errors from interplay effects. All of these effects may be of clinical importance. Here we present a method to compute delivered dose distributions for each treatment beam and fraction, which explicitly incorporates synchronized real-time patient motion data and real-time fluence and machine configuration data. This synchronized dynamic dose reconstruction method properly accounts for the two primary classes of errors that arise from delivering IMRT with an MLC: (a) Interplay errors between target volume motion and MLC motion, and (b) Implementation errors, such as dropped segments, dose over/under shoot, faulty leaf motors, tongue-and-groove effect, rounded leaf ends, and communications delays. These reconstructed dose fractions can then be combined to produce high-quality determinations of the dose distribution actually received to date, from which individualized adaptive treatment strategies can be determined

Design and Hardware Implementation of a New Chaotic Secure Communication Technique.

Directory of Open Access Journals (Sweden)

Li Xiong

Full Text Available In this paper, a scheme for chaotic modulation secure communication is proposed based on chaotic synchronization of an improved Lorenz system. For the first time, the intensity limit and stability of the transmitted signal, the characteristics of broadband and the requirements for accuracy of electronic components are presented by Multisim simulation. In addition, some improvements are made on the measurement method and the proposed experimental circuit in order to facilitate the experiments of chaotic synchronization, chaotic non-synchronization, experiment without signal and experiment with signal. To illustrate the effectiveness of the proposed scheme, some numerical simulations are presented. Then, the proposed chaotic secure communication circuit is implemented through analog electronic circuit, which is characterized by its high accuracy and good robustness.

Design and Hardware Implementation of a New Chaotic Secure Communication Technique.

Science.gov (United States)

Xiong, Li; Lu, Yan-Jun; Zhang, Yong-Fang; Zhang, Xin-Guo; Gupta, Parag

2016-01-01

In this paper, a scheme for chaotic modulation secure communication is proposed based on chaotic synchronization of an improved Lorenz system. For the first time, the intensity limit and stability of the transmitted signal, the characteristics of broadband and the requirements for accuracy of electronic components are presented by Multisim simulation. In addition, some improvements are made on the measurement method and the proposed experimental circuit in order to facilitate the experiments of chaotic synchronization, chaotic non-synchronization, experiment without signal and experiment with signal. To illustrate the effectiveness of the proposed scheme, some numerical simulations are presented. Then, the proposed chaotic secure communication circuit is implemented through analog electronic circuit, which is characterized by its high accuracy and good robustness.

Pinning synchronization of delayed complex dynamical networks with nonlinear coupling

Science.gov (United States)

Cheng, Ranran; Peng, Mingshu; Yu, Weibin

2014-11-01

In this paper, we find that complex networks with the Watts-Strogatz or scale-free BA random topological architecture can be synchronized more easily by pin-controlling fewer nodes than regular systems. Theoretical analysis is included by means of Lyapunov functions and linear matrix inequalities (LMI) to make all nodes reach complete synchronization. Numerical examples are also provided to illustrate the importance of our theoretical analysis, which implies that there exists a gap between the theoretical prediction and numerical results about the minimum number of pinning controlled nodes.

Synchronization ability of coupled cell-cycle oscillators in changing environments

Science.gov (United States)

2012-01-01

Background The biochemical oscillator that controls periodic events during the Xenopus embryonic cell cycle is centered on the activity of CDKs, and the cell cycle is driven by a protein circuit that is centered on the cyclin-dependent protein kinase CDK1 and the anaphase-promoting complex (APC). Many studies have been conducted to confirm that the interactions in the cell cycle can produce oscillations and predict behaviors such as synchronization, but much less is known about how the various elaborations and collective behavior of the basic oscillators can affect the robustness of the system. Therefore, in this study, we investigate and model a multi-cell system of the Xenopus embryonic cell cycle oscillators that are coupled through a common complex protein, and then analyze their synchronization ability under four different external stimuli, including a constant input signal, a square-wave periodic signal, a sinusoidal signal and a noise signal. Results Through bifurcation analysis and numerical simulations, we obtain synchronization intervals of the sensitive parameters in the individual oscillator and the coupling parameters in the coupled oscillators. Then, we analyze the effects of these parameters on the synchronization period and amplitude, and find interesting phenomena, e.g., there are two synchronization intervals with activation coefficient in the Hill function of the activated CDK1 that activates the Plk1, and different synchronization intervals have distinct influences on the synchronization period and amplitude. To quantify the speediness and robustness of the synchronization, we use two quantities, the synchronization time and the robustness index, to evaluate the synchronization ability. More interestingly, we find that the coupled system has an optimal signal strength that maximizes the synchronization index under different external stimuli. Simulation results also show that the ability and robustness of the synchronization for the square

Content-based intermedia synchronization

Science.gov (United States)

Oh, Dong-Young; Sampath-Kumar, Srihari; Rangan, P. Venkat

1995-03-01

Inter-media synchronization methods developed until now have been based on syntactic timestamping of video frames and audio samples. These methods are not fully appropriate for the synchronization of multimedia objects which may have to be accessed individually by their contents, e.g. content-base data retrieval. We propose a content-based multimedia synchronization scheme in which a media stream is viewed as hierarchial composition of smaller objects which are logically structured based on the contents, and the synchronization is achieved by deriving temporal relations among logical units of media object. content-based synchronization offers several advantages such as, elimination of the need for time stamping, freedom from limitations of jitter, synchronization of independently captured media objects in video editing, and compensation for inherent asynchronies in capture times of video and audio.

The Lived Experience of In-Service Teachers Using Synchronous Technology: A Phenomenological Study

Science.gov (United States)

Vasquez, Sarah T.

2017-01-01

Unlike most online professional development opportunities, synchronous technology affords immediate communications for discussion and feedback while interacting with participants simultaneously through text, audio, video, and screen sharing. The purpose of this study is to find answers to meet the practical need to inform, design, and implement…

Longitudinal development of communication in children with cerebral palsy between 24 and 53 months: Predicting speech outcomes.

Science.gov (United States)

Hustad, Katherine C; Allison, Kristen M; Sakash, Ashley; McFadd, Emily; Broman, Aimee Teo; Rathouz, Paul J

2017-08-01

To determine whether communication at 2 years predicted communication at 4 years in children with cerebral palsy (CP); and whether the age a child first produces words imitatively predicts change in speech production. 30 children (15 males) with CP participated and were seen 5 times at 6-month intervals between 24 and 53 months (mean age at time 1 = 26.9 months (SD 1.9)). Variables were communication classification at 24 and 53 months, age that children were first able to produce words imitatively, single-word intelligibility, and longest utterance produced. Communication at 24 months was highly predictive of abilities at 53 months. Speaking earlier led to faster gains in intelligibility and length of utterance and better outcomes at 53 months than speaking later. Inability to speak at 24 months indicates greater speech and language difficulty at 53 months and a strong need for early communication intervention.

A precise time synchronization method for 5G based on radio-over-fiber network with SDN controller

Science.gov (United States)

He, Linkuan; Wei, Baoguo; Yang, Hui; Yu, Ao; Wang, Zhengyong; Zhang, Jie

2018-02-01

There is an increasing demand on accurate time synchronization with the growing bandwidth of network service for 5G. In 5G network, it's necessary for base station to achieve accurate time synchronization to guarantee the quality of communication. In order to keep accuracy time for 5G network, we propose a time synchronization system for satellite ground station based on radio-over-fiber network (RoFN) with software defined optical network (SDON) controller. The advantage of this method is to improve the accuracy of time synchronization of ground station. The IEEE 1588 time synchronization protocol can solve the problems of high cost and lack of precision. However, in the process of time synchronization, distortion exists during the transmission of digital time signal. RoF uses analog optical transmission links and therefore analog transmission can be implemented among ground stations instead of digital transmission, which means distortion and bandwidth waste in the process of digital synchronization can be avoided. Additionally, the thought of SDN, software defined network, can optimize RoFN with centralized control and simplifying base station. Related simulation had been carried out to prove its superiority.

Fast Self-Synchronization between LowVoltage Microgrid and Inverter using Virtual Synchronous Converter

Directory of Open Access Journals (Sweden)

Md Ruhul Amin

2017-12-01

Full Text Available In this paper, a fast self-synchronization known as virtual synchronous converter (VSCon between single-phase microgrid and inverter in low-voltage microgrid, has been developed in Matlab/Simulink. The idea is to any phase locked loop (PLL circuit for inverter-microgrid synchronization in order to improve the synchronization time. As known, it is difficult and lengthy process to tune the PLL gain parameters to reach suitable performance for synchronizing among the voltage, phase-angle and frequency between them. Due to this problem, a fast self synchronization technique is needed in order to minimize the time losses at the microgrid connection. Therefore, the VSCon has been developed which is based on the synchronous generator mathematical model but in virtual environment representation. It has been applied in the inverter control for generating switching pattern to the inverter switches in order to respond to the grid voltage for improve the synchronization. For a prove of concept, several simulation tests in MATLAB models have been conducted, in order to see the effectiveness of this VSCon. First test has been conducted, when a 240V, 50Hz frequency grid source is used for observing the self-synchronization the system with the power flows output. Furthermore, the next test is conducted when the grid frequency is changed from the rated frequency at 50Hz to 51Hz and the result shows the VSCon in inverter control takes nearly 40ms to synchronize to this new frequency value. The test on grid phase-angle delay also been tested when ac grid voltage has 150 phase delay. As from all the results, the improved inverter control with VSCon structure is able to have fast and self-synchronized between the invertergrid connection before the power from the inverter can be transferred.

The formation of synchronization cliques during the development of modular neural networks

International Nuclear Information System (INIS)

Fuchs, Einat; Ayali, Amir; Ben-Jacob, Eshel; Boccaletti, Stefano

2009-01-01

Modular organization is a special feature shared by many biological and social networks alike. It is a hallmark for systems exhibiting multitasking, in which individual tasks are performed by separated and yet coordinated functional groups. Understanding how networks of segregated modules develop to support coordinated multitasking functionalities is the main topic of the current study. Using simulations of biologically inspired neuronal networks during development, we study the formation of functional groups (cliques) and inter-neuronal synchronization. The results indicate that synchronization cliques first develop locally according to the explicit network topological organization. Later on, at intermediate connectivity levels, when networks have both local segregation and long-range integration, new synchronization cliques with distinctive properties are formed. In particular, by defining a new measure of synchronization centrality, we identify at these developmental stages dominant neurons whose functional centrality largely exceeds the topological one. These are generated mainly in a few dominant clusters that become the centers of the newly formed synchronization cliques. We show that by the local synchronization properties at the very early developmental stages, it is possible to predict with high accuracy which clusters will become dominant in later stages of network development

Synchronization of Multipoint Hoists

Science.gov (United States)

A contractor has conceived an electrohydraulic feedback system that will provide position synchronization of four aircraft cargo hoists. To... synchronized hoist system. Test results show that the feedback system concept provides adequate synchronization control; i.e., the platform pitch and roll

Asynchronous error-correcting secure communication scheme based on fractional-order shifting chaotic system

Science.gov (United States)

Chao, Luo

2015-11-01

In this paper, a novel digital secure communication scheme is firstly proposed. Different from the usual secure communication schemes based on chaotic synchronization, the proposed scheme employs asynchronous communication which avoids the weakness of synchronous systems and is susceptible to environmental interference. Moreover, as to the transmission errors and data loss in the process of communication, the proposed scheme has the ability to be error-checking and error-correcting in real time. In order to guarantee security, the fractional-order complex chaotic system with the shifting of order is utilized to modulate the transmitted signal, which has high nonlinearity and complexity in both frequency and time domains. The corresponding numerical simulations demonstrate the effectiveness and feasibility of the scheme.

Robust output synchronization of heterogeneous nonlinear agents in uncertain networks.

Science.gov (United States)

Yang, Xi; Wan, Fuhua; Tu, Mengchuan; Shen, Guojiang

2017-11-01

This paper investigates the global robust output synchronization problem for a class of nonlinear multi-agent systems. In the considered setup, the controlled agents are heterogeneous and with both dynamic and parametric uncertainties, the controllers are incapable of exchanging their internal states with the neighbors, and the communication network among agents is defined by an uncertain simple digraph. The problem is pursued via nonlinear output regulation theory and internal model based design. For each agent, the input-driven filter and the internal model compose the controller, and the decentralized dynamic output feedback control law is derived by using backstepping method and the modified dynamic high-gain technique. The theoretical result is applied to output synchronization problem for uncertain network of Lorenz-type agents. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

LONG-TERM STABLE EQUILIBRIA FOR SYNCHRONOUS BINARY ASTEROIDS

International Nuclear Information System (INIS)

Jacobson, Seth A.; Scheeres, Daniel J.

2011-01-01

Synchronous binary asteroids may exist in a long-term stable equilibrium, where the opposing torques from mutual body tides and the binary YORP (BYORP) effect cancel. Interior of this equilibrium, mutual body tides are stronger than the BYORP effect and the mutual orbit semimajor axis expands to the equilibrium; outside of the equilibrium, the BYORP effect dominates the evolution and the system semimajor axis will contract to the equilibrium. If the observed population of small (0.1-10 km diameter) synchronous binaries are in static configurations that are no longer evolving, then this would be confirmed by a null result in the observational tests for the BYORP effect. The confirmed existence of this equilibrium combined with a shape model of the secondary of the system enables the direct study of asteroid geophysics through the tidal theory. The observed synchronous asteroid population cannot exist in this equilibrium if described by the canonical 'monolithic' geophysical model. The 'rubble pile' geophysical model proposed by Goldreich and Sari is sufficient, however it predicts a tidal Love number directly proportional to the radius of the asteroid, while the best fit to the data predicts a tidal Love number inversely proportional to the radius. This deviation from the canonical and Goldreich and Sari models motivates future study of asteroid geophysics. Ongoing BYORP detection campaigns will determine whether these systems are in an equilibrium, and future determination of secondary shapes will allow direct determination of asteroid geophysical parameters.

Circuit Implementation, Synchronization of Multistability, and Image Encryption of a Four-Wing Memristive Chaotic System

Directory of Open Access Journals (Sweden)

Guangya Peng

2018-01-01

Full Text Available The four-wing memristive chaotic system used in synchronization is applied to secure communication which can increase the difficulty of deciphering effectively and enhance the security of information. In this paper, a novel four-wing memristive chaotic system with an active cubic flux-controlled memristor is proposed based on a Lorenz-like circuit. Dynamical behaviors of the memristive system are illustrated in terms of Lyapunov exponents, bifurcation diagrams, coexistence Poincaré maps, coexistence phase diagrams, and attraction basins. Besides, the modular equivalent circuit of four-wing memristive system is designed and the corresponding results are observed to verify its accuracy and rationality. A nonlinear synchronization controller with exponential function is devised to realize synchronization of the coexistence of multiple attractors, and the synchronization control scheme is applied to image encryption to improve secret key space. More interestingly, considering different influence of multistability on encryption, the appropriate key is achieved to enhance the antideciphering ability.

Optimal operating conditions for external cavity semiconductor laser optical chaos communication system

International Nuclear Information System (INIS)

Priyadarshi, S; Pierce, I; Hong, Y; Shore, K A

2012-01-01

In optical chaos communications a message is masked in the noise-like broadband output of a chaotic transmitter laser, and message recovery is enabled through the synchronization of the transmitter and the (chaotic) receiver laser. Key issues are to identify the laser operating conditions which provide the highest quality synchronization conditions and those which provide optimized message extraction. In general such operating conditions are not coincident. In this paper numerical simulations are performed with the aim of identifying a regime of operation where the highest quality synchronization and optimizing message extraction efficiency are achieved simultaneously. Use of such an operating regime will facilitate practical deployment of optical chaos communications systems without the need for re-adjustment of laser operating conditions in the field. (paper)

Synchronization scenarios in the Winfree model of coupled oscillators

Science.gov (United States)

Gallego, Rafael; Montbrió, Ernest; Pazó, Diego

2017-10-01

Fifty years ago Arthur Winfree proposed a deeply influential mean-field model for the collective synchronization of large populations of phase oscillators. Here we provide a detailed analysis of the model for some special, analytically tractable cases. Adopting the thermodynamic limit, we derive an ordinary differential equation that exactly describes the temporal evolution of the macroscopic variables in the Ott-Antonsen invariant manifold. The low-dimensional model is then thoroughly investigated for a variety of pulse types and sinusoidal phase response curves (PRCs). Two structurally different synchronization scenarios are found, which are linked via the mutation of a Bogdanov-Takens point. From our results, we infer a general rule of thumb relating pulse shape and PRC offset with each scenario. Finally, we compare the exact synchronization threshold with the prediction of the averaging approximation given by the Kuramoto-Sakaguchi model. At the leading order, the discrepancy appears to behave as an odd function of the PRC offset.

Cell Division Synchronization

Science.gov (United States)

The report summarizes the progress in the design and construction of automatic equipment for synchronizing cell division in culture by periodic...Concurrent experiments in hypothermic synchronization of algal cell division are reported.

Control-oriented approaches to anticipating synchronization of chaotic deterministic ratchets

Energy Technology Data Exchange (ETDEWEB)

Xu Shiyun [State Key Lab for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China)], E-mail: xushiyun@pku.edu.cn; Yang Ying [State Key Lab for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China)], E-mail: yy@mech.pku.edu.cn; Song Lei [State Key Lab for Turbulence and Complex Systems, Department of Mechanics and Aerospace Engineering, College of Engineering, Peking University, Beijing 100871 (China)

2009-06-15

In virtue of techniques derived from nonlinear control system theory, we establish conditions under which one could obtain anticipating synchronization between two periodically driven deterministic ratchets that are able to exhibit directed transport with a finite velocity. Criteria are established in order to guarantee the anticipating synchronization property of such systems as well as characterize phase space dynamics of the ratchet transporting behaviors. These results allow one to predict the chaotic direct transport features of particles on a ratchet potential using a copy of the same system that performs as a slave, which are verified through numerical simulation.

Synchronization dynamics of two different dynamical systems

International Nuclear Information System (INIS)

Luo, Albert C.J.; Min Fuhong

2011-01-01

Highlights: → Synchronization dynamics of two distinct dynamical systems. → Synchronization, de-synchronization and instantaneous synchronization. → A controlled pendulum synchronizing with the Duffing oscillator. → Synchronization invariant set. → Synchronization parameter map. - Abstract: In this paper, synchronization dynamics of two different dynamical systems is investigated through the theory of discontinuous dynamical systems. The necessary and sufficient conditions for the synchronization, de-synchronization and instantaneous synchronization (penetration or grazing) are presented. Using such a synchronization theory, the synchronization of a controlled pendulum with the Duffing oscillator is systematically discussed as a sampled problem, and the corresponding analytical conditions for the synchronization are presented. The synchronization parameter study is carried out for a better understanding of synchronization characteristics of the controlled pendulum and the Duffing oscillator. Finally, the partial and full synchronizations of the controlled pendulum with periodic and chaotic motions are presented to illustrate the analytical conditions. The synchronization of the Duffing oscillator and pendulum are investigated in order to show the usefulness and efficiency of the methodology in this paper. The synchronization invariant domain is obtained. The technique presented in this paper should have a wide spectrum of applications in engineering. For example, this technique can be applied to the maneuvering target tracking, and the others.

Peri-operative communication patterns and media usage--implications for systems design.

Science.gov (United States)

Karlsen, Ero S; Toussaint, Pieter Jelle

2010-01-01

Inter-hospital communication amounts for a great deal of clinicians' work time. While communication is essential to coordinate care, it can also be time consuming and interruptive, and breakdown in communication is an important source of medical errors. One contributor to the interruptive nature of communication is the use of synchronous media, and there is clearly a potential for novel technologies. To assess communication patterns and media usage we performed an ethnographic field study in the peri-operative environment at a Norwegian hospital, as well as interviews with nurses. We analyze the results with regards to choice of media, characteristics of the conversations taking place and meta-messages, and account for addressing, obtrusiveness and information richness in the message exchanges. We find a relative high degree of interruptiveness in communication, and ascribe it to 1) a lack of situational awareness between locations in the peri-operative domain, as well as 2) use of synchronous media. This suggests that design of novel technology for intra-hospital communication should aim at supporting sender-receiver awareness and signaling of availability.

Do the big-five personality traits predict empathic listening and assertive communication?

OpenAIRE

Sims, Ceri M.

2016-01-01

As personality traits can influence important social outcomes, the current research investigated whether the Big-Five had predictive influences on communication competences of active-empathic listening (AEL) and assertiveness. A sample of 245 adults of various ages completed the self-report scales. Both Agreeableness and Openness uniquely predicted AEL. Extraversion had the biggest influence onassertiveness but did not uniquely explain AEL variance. Conscientiousness and Neuroticism had small...

FPGA based fast synchronous serial multi-wire links synchronization

Science.gov (United States)

Pozniak, Krzysztof T.

2013-10-01

The paper debates synchronization method of multi-wire, serial link of constant latency, by means of pseudo-random numbers generators. The solution was designed for various families of FPGA circuits. There were debated synchronization algorithm and functional structure of parameterized transmitter and receiver modules. The modules were realized in VHDL language in a behavioral form.

Peer Observation, Feedback and Reflection for Development of Practice in Synchronous Online Teaching

Science.gov (United States)

Jones, Mark H.; Gallen, Anne-Marie

2016-01-01

Peer observation of teaching is an established developmental tool in face-to-face settings. While there have been studies into peer observation as applied to asynchronous online teaching, less is known about its application to teaching online using synchronous communication systems. We describe a small-scale study of an online peer observation…

Exploiting Schemas in Data Synchronization

DEFF Research Database (Denmark)

Foster, J. Nathan; Greenwald, Michael B.; Kirkegaard, Christian

2005-01-01

Increased reliance on optimistic data replication has led to burgeoning interest in tools and frameworks for disconnected updates to replicated data.We have implemented a generic synchronization framework, called HARMONY, that can be used to build state-based synchronizers for a wide variety...... of tree-structureddata formats. A novel feature of this framework is that the synchronization process - in particular, the recognition of conflicts - is driven by the schema of the structures being synchronized.We formalize HARMONY's synchronization algorithm, state a simple and intuitive specification......, and illustrate, using simple address books as a case study, how it can be used to synchronize trees representing a variety of specific forms of applicationdata, including sets, records, tuples, and relations....

Novel Sensorless Six-Step Communication Strategy for a Surface Permanent Magnet Synchronous Motor with DC Link Measurement

DEFF Research Database (Denmark)

Munteanu, A.; Agarlita, S. C.; Blaabjerg, Frede

2012-01-01

The present paper introduces a novel six-step commutation strategy for sensorless control applied for a surface permanent magnet synchronous motor that implies only dc link measurement (battery current and battery voltage). The control strategy makes use of a modified I-f starting procedure and t......-crossing of the back-emf are obtained from an observer that uses both current and battery voltage. The case study is represented by a surface permanent magnet synchronous motor prototype (6 /8 configuration), designed for the automotive air conditioning compressor drive....

Using Web-Based, Group Communication Systems to Support Case Study Learning at a Distance

Directory of Open Access Journals (Sweden)

Liam Rourke

2002-10-01

Full Text Available This study explored the capacity of Web-based, group communication systems to support case-based teaching and learning. Eleven graduate students studying at a distance were divided into three groups to collaborate on a case study using either a synchronous voice, an asynchronous voice, or a synchronous text communication system. Participants kept a detailed log of the time they spent on various activities, wrote a 1,500-word reflection on their experience, and participated in a group interview. Analysis of these data reveals that each group supplemented the system that had been assigned to them with additional communication systems in order to complete the project. Each of these systems were used strategically: email was used to share files and arrange meetings, and synchronous voice systems were used to brainstorm and make decisions. Learning achievement was high across groups and students enjoyed collaborating with others on a concrete task.

A study on synchronously whirling motion of hydrodynamic journal bearings

International Nuclear Information System (INIS)

Rho, Byoung Hoo; Kim, Kyung Woong

2001-01-01

In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing

A study on synchronously whirling motion of hydrodynamic journal bearings

Energy Technology Data Exchange (ETDEWEB)

Rho, Byoung Hoo; Kim, Kyung Woong [Korea Advanced Institute of Science and Technology, Taejon (Korea, Republic of)

2001-09-01

In this paper, a control algorithm which is synchronously excitation the bearing with whirl speed of rotor is employed to suppress the whirl instability and unbalance response of the rotor-bearing system. Also, the cavitation algorithm implementing the Jakobsson-Floberg-Olsson boundary condition is adopted to predict cavitation regions in the fluid film more accurately than a conventional analysis with the Renolds condition. The stabilities and unbalance responses of the rotor-bearing system are investigated for various control gains and phase differences between the bearing and journal motion. It is shown that the unbalance response of the system can be greatly improved by synchronous control of the bearing, and there is an optimum phase difference, which gives the minimum unbalance response of the system, for given operating condition. It is also found that the onset speed of the instability can be greatly increased by synchronous control of the bearing.

Blending Synchronous Face-to-Face and Computer-Supported Cooperative Learning in a Hybrid Doctoral Seminar

Science.gov (United States)

Roseth, Cary; Akcaoglu, Mete; Zellner, Andrea

2013-01-01

Online education is often assumed to be synonymous with asynchronous instruction, existing apart from or supplementary to face-to-face instruction in traditional bricks-and-mortar classrooms. However, expanding access to computer-mediated communication technologies now make new models possible, including distance learners synchronous online…

Asynchronized synchronous machines

CERN Document Server

Botvinnik, M M

1964-01-01

Asynchronized Synchronous Machines focuses on the theoretical research on asynchronized synchronous (AS) machines, which are "hybrids” of synchronous and induction machines that can operate with slip. Topics covered in this book include the initial equations; vector diagram of an AS machine; regulation in cases of deviation from the law of full compensation; parameters of the excitation system; and schematic diagram of an excitation regulator. The possible applications of AS machines and its calculations in certain cases are also discussed. This publication is beneficial for students and indiv

Adaptive two-degree-of-freedom PI for speed control of permanent magnet synchronous motor based on fractional order GPC.

Science.gov (United States)

Qiao, Wenjun; Tang, Xiaoqi; Zheng, Shiqi; Xie, Yuanlong; Song, Bao

2016-09-01

In this paper, an adaptive two-degree-of-freedom (2Dof) proportional-integral (PI) controller is proposed for the speed control of permanent magnet synchronous motor (PMSM). Firstly, an enhanced just-in-time learning technique consisting of two novel searching engines is presented to identify the model of the speed control system in a real-time manner. Secondly, a general formula is given to predict the future speed reference which is unavailable at the interval of two bus-communication cycles. Thirdly, the fractional order generalized predictive control (FOGPC) is introduced to improve the control performance of the servo drive system. Based on the identified model parameters and predicted speed reference, the optimal control law of FOGPC is derived. Finally, the designed 2Dof PI controller is auto-tuned by matching with the optimal control law. Simulations and real-time experimental results on the servo drive system of PMSM are provided to illustrate the effectiveness of the proposed strategy. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

Analysis of synchronized regimes for injection-locked spin-transfer nano-oscillators

Energy Technology Data Exchange (ETDEWEB)

D' Aquino, M., E-mail: daquino@uniparthenope.it [Department of Technology, University of Napoli ' Parthenope' , 80143 Napoli (Italy); Serpico, C. [Department of Engineering, University of Napoli Federico II, 80125 Napoli (Italy); Bonin, R. [Politecnico di Torino - Sede di Verres, 11029 Verres (Aosta) (Italy); Bertotti, G. [Istituto Nazionale di Ricerca Metrologica, 10135 Torino (Italy); Mayergoyz, I.D. [ECE Dept. and UMIACS, University of Maryland, College Park, MD 20742 (United States)

2012-05-01

The large-angle magnetization dynamics of an injection-locked spin-transfer nano-oscillator (STNO) is studied. The magnetic system is subject to the action of time-varying spin-polarized currents and external magnetic fields. The uniform mode theory is developed and describes the hysteretic synchronization mechanism in terms of bifurcations of equilibria and limit cycles of appropriate dynamical systems. Analytical predictions of control parameters for the synchronization between the magnetization self-oscillation and the external microwave excitations (current, field) are provided. The effect of temperature on the locking band and the hysteretic character of the oscillation response is analyzed. An analytical approach is developed to determine the thermally induced sidebands in the power spectral density of phase-locked oscillations as a function of control parameters. The analytical predictions are in good agreement with the results of numerical simulations.

Control of non-conventional synchronous motors

CERN Document Server

Louis, Jean-Paul

2013-01-01

Classical synchronous motors are the most effective device to drive industrial production systems and robots with precision and rapidity. However, numerous applications require efficient controls in non-conventional situations. Firstly, this is the case with synchronous motors supplied by thyristor line-commutated inverters, or with synchronous motors with faults on one or several phases. Secondly, many drive systems use non-conventional motors such as polyphase (more than three phases) synchronous motors, synchronous motors with double excitation, permanent magnet linear synchronous motors,

Anti-synchronization of chaotic oscillators

International Nuclear Information System (INIS)

Kim, Chil-Min; Rim, Sunghwan; Kye, Won-Ho; Ryu, Jung-Wan; Park, Young-Jai

2003-01-01

We have observed anti-synchronization phenomena in coupled identical chaotic oscillators. Anti-synchronization can be characterized by the vanishing of the sum of relevant variables. We have qualitatively analyzed its base mechanism by using the dynamics of the difference and the sum of the relevant variables in coupled chaotic oscillators. Near the threshold of the synchronization and anti-synchronization transition, we have obtained the novel characteristic relation

Secure communications of CAP-4 and OOK signals over MMF based on electro-optic chaos.

Science.gov (United States)

Ai, Jianzhou; Wang, Lulu; Wang, Jian

2017-09-15

Chaos-based secure communication can provide a high level of privacy in data transmission. Here, we experimentally demonstrate secure signal transmission over two kinds of multimode fiber (MMF) based on electro-optic intensity chaos. High-quality synchronization is achieved in an electro-optic feedback configuration. Both 5  Gbit/s carrier-less amplitude/phase (CAP-4) modulation and 10  Gbit/s on-off key (OOK) signals are recovered efficiently in electro-optic chaos-based communication systems. Degradations of chaos synchronization and communication system due to mismatch of various hardware keys are also discussed.

Synchronization of random bit generators based on coupled chaotic lasers and application to cryptography.

Science.gov (United States)

Kanter, Ido; Butkovski, Maria; Peleg, Yitzhak; Zigzag, Meital; Aviad, Yaara; Reidler, Igor; Rosenbluh, Michael; Kinzel, Wolfgang

2010-08-16

Random bit generators (RBGs) constitute an important tool in cryptography, stochastic simulations and secure communications. The later in particular has some difficult requirements: high generation rate of unpredictable bit strings and secure key-exchange protocols over public channels. Deterministic algorithms generate pseudo-random number sequences at high rates, however, their unpredictability is limited by the very nature of their deterministic origin. Recently, physical RBGs based on chaotic semiconductor lasers were shown to exceed Gbit/s rates. Whether secure synchronization of two high rate physical RBGs is possible remains an open question. Here we propose a method, whereby two fast RBGs based on mutually coupled chaotic lasers, are synchronized. Using information theoretic analysis we demonstrate security against a powerful computational eavesdropper, capable of noiseless amplification, where all parameters are publicly known. The method is also extended to secure synchronization of a small network of three RBGs.

SynUTC - high precision time synchronization over ethernet networks

CERN Document Server

Höller, R; Horauer, M; Kerö, N; Schmid, U; Schossmaier, K

2002-01-01

This article describes our SynUTC (Synchronized Universal Time Coordinated) technology, which enables high-accuracy distribution of GPS time and time synchronization of network nodes connected via standard Ethernet LANs. By means of exchanging data packets in conjunction with moderate hardware support at nodes and switches, an overall worst-case accuracy in the range of some 100 ns can be achieved, with negligible communication overhead. Our technology thus improves the 1 ms-range accuracy achievable by conventional, software-based approaches like NTP by 4 orders of magnitude. Applications can use the high-accuracy global time provided by SynUTC for event timestamping and event generation both at hardware and software level. SynUTC is based upon inserting highly accurate time information into dedicated data packets at the media-independent interface (MII) between the physical layer transceiver and the network controller upon packet transmission and reception, respectively. As a consequence, every node has acc...

The synchronization method for distributed small satellite SAR

Science.gov (United States)

Xing, Lei; Gong, Xiaochun; Qiu, Wenxun; Sun, Zhaowei

2007-11-01

One of critical requirement for distributed small satellite SAR is the trigger time precision when all satellites turning on radar loads. This trigger operation is controlled by a dedicated communication tool or GPS system. In this paper a hardware platform is proposed which has integrated navigation, attitude control, and data handling system together. Based on it, a probabilistic synchronization method is proposed for SAR time precision requirement with ring architecture. To simplify design of transceiver, half-duplex communication way is used in this method. Research shows that time precision is relevant to relative frequency drift rate, satellite number, retry times, read error and round delay length. Installed with crystal oscillator short-term stability 10 -11 magnitude, this platform can achieve and maintain nanosecond order time error with a typical three satellites formation experiment during whole operating process.

Coexistence and switching of anticipating synchronization and lag synchronization in an optical system

International Nuclear Information System (INIS)

Wu, Liang; Zhu, Shiqun

2003-01-01

The chaotic synchronization between two bi-directionally coupled external cavity single-mode semiconductor lasers is investigated. Numerical simulation shows that anticipating synchronization and lag synchronization coexist and switch between each other in certain parameter regime. The anticipating time with different effects that were discussed quite differently in the previous theoretical analysis and experimental observation is determined by the involved parameters in the system

Adaptive Backoff Synchronization Techniques

Science.gov (United States)

1989-07-01

Percentage of synchronization and non- synchronisation references that cause invalidations in directory schemes with 2, 3, 4, 5, and 64 pointers...processors to arrive. The slight relative increase of synchronisation overhead in all cases when going from two to five pointers is because synchronization ...MASSACHUSETTS INSTITUTE OF TECHNOLOGY VLSI PUBLICATIONS q~JU VLSI Memo No. 89-547 It July 1989 Adaptive Backoff Synchronization Techniques Anant

Interprocess Communication in Highly Distributed Systems - A Workshop Report - 20 to 22, November 1978.

Science.gov (United States)

1979-12-01

semaphores , are implemented at the microcode level, and are available for system and user tasks. In addition to these basic synchronization primitives ... Synchronizations SignaLLing, and FLow Control 4) Theory and Formalism 5) Hardware and Primitives 6) Programming Issues However, as often (usually...building blocks. Primitives for the creation, synchronization , addressinq and communication of processes have in the past onLy been generaLly avaiLabLe to

Synchronicity and Leadership

NARCIS (Netherlands)

Merry, Philip

2017-01-01

LAY SUMMARY SYNCHRONICITY AND LEADERSHIP TILBURG PHD DISSERTATION, PHILIP MERRY World’s First PhD to Research Synchronicity And Leadership Using Grounded Theory OUT OF THE BLUE COINCIDENCES: research topic Most people have had the experience of thinking of someone and then, almost magically have

Synchronous implementation of optoelectronic NOR and XNOR logic gates using parallel synchronization of three chaotic lasers

International Nuclear Information System (INIS)

Yan Sen-Lin

2014-01-01

The parallel synchronization of three chaotic lasers is used to emulate optoelectronic logic NOR and XNOR gates via modulating the light and the current. We deduce a logical computational equation that governs the chaotic synchronization, logical input, and logical output. We construct fundamental gates based on the three chaotic lasers and define the computational principle depending on the parallel synchronization. The logic gate can be implemented by appropriately synchronizing two chaotic lasers. The system shows practicability and flexibility because it can emulate synchronously an XNOR gate, two NOR gates, and so on. The synchronization can still be deteceted when mismatches exist with a certain range. (general)

Data-derived symbol synchronization of MASK and QASK signals. [Multilevel and Quadrature Amplitude Shift Keying

Science.gov (United States)

Simon, M. K.

1975-01-01

Much has been said in the literature regarding the problem of establishing symbol synchronization in binary baseband digital communication systems. By comparison, the literature contains little information relating to the extraction of symbol sync from multilevel baseband data. With the recent interest in multilevel amplitude-shift keying (MASK) and quadrature amplitude-shift keying (QASK) as signaling techniques for multilevel digital communications systems, the problem of providing symbol synchronization in the receivers of such systems becomes paramount. This paper presents a technique for extracting symbol sync from a MASK or QASK signal which has been transmitted over an infinite-bandwidth white Gaussian noise channel. The scheme is essentially a generalization of the data transition tracking loop (DTTL) which has heretofore been used in PSK systems. The performance of the loop is analyzed in terms of its mean-squared symbol sync jitter and its effects on the data detection process in MASK and QASK systems.

Bidirectional communication using delay coupled chaotic directly ...

Indian Academy of Sciences (India)

Corresponding author. ... 30 September 2009. Abstract. Chaotic synchronization of two directly modulated semiconductor lasers with ... For InGaAsP lasers used in optical communication systems, the nonlinear gain re- duction is very strong and its ...

Managing Communications with Experts in Geographically Distributed Collaborative Networks

Science.gov (United States)

2009-03-01

communication. Chat and instant messaging supports enhanced group communication and normally includes features to save this synchronous communication for...means to find and receive information. 5. Online Instruction eLearning : The flow of knowledge is important to a CoP. eLearning contributes to this by...providing a cost efficient way of promoting knowledge flow in a more traditional manner. It has evolved from earlier versions (i.e., computer or

Synchronization stability and pattern selection in a memristive neuronal network

Science.gov (United States)

Wang, Chunni; Lv, Mi; Alsaedi, Ahmed; Ma, Jun

2017-11-01

Spatial pattern formation and selection depend on the intrinsic self-organization and cooperation between nodes in spatiotemporal systems. Based on a memory neuron model, a regular network with electromagnetic induction is proposed to investigate the synchronization and pattern selection. In our model, the memristor is used to bridge the coupling between the magnetic flux and the membrane potential, and the induction current results from the time-varying electromagnetic field contributed by the exchange of ion currents and the distribution of charged ions. The statistical factor of synchronization predicts the transition of synchronization and pattern stability. The bifurcation analysis of the sampled time series for the membrane potential reveals the mode transition in electrical activity and pattern selection. A formation mechanism is outlined to account for the emergence of target waves. Although an external stimulus is imposed on each neuron uniformly, the diversity in the magnetic flux and the induction current leads to emergence of target waves in the studied network.

Synchronization stability and pattern selection in a memristive neuronal network.

Science.gov (United States)

Wang, Chunni; Lv, Mi; Alsaedi, Ahmed; Ma, Jun

2017-11-01

Spatial pattern formation and selection depend on the intrinsic self-organization and cooperation between nodes in spatiotemporal systems. Based on a memory neuron model, a regular network with electromagnetic induction is proposed to investigate the synchronization and pattern selection. In our model, the memristor is used to bridge the coupling between the magnetic flux and the membrane potential, and the induction current results from the time-varying electromagnetic field contributed by the exchange of ion currents and the distribution of charged ions. The statistical factor of synchronization predicts the transition of synchronization and pattern stability. The bifurcation analysis of the sampled time series for the membrane potential reveals the mode transition in electrical activity and pattern selection. A formation mechanism is outlined to account for the emergence of target waves. Although an external stimulus is imposed on each neuron uniformly, the diversity in the magnetic flux and the induction current leads to emergence of target waves in the studied network.

Design and realization of multithread CAMAC communication server software based on Winsock

International Nuclear Information System (INIS)

Zhang Xia

2002-01-01

The author describes the CAMAC communication server software which applies Winsock and multithread techniques. The design method of the whole software is given. The realization of network communication service and the synchronization problem of multithread are introduced in detail

Classification of plum spirit drinks by synchronous fluorescence spectroscopy.

Science.gov (United States)

Sádecká, J; Jakubíková, M; Májek, P; Kleinová, A

2016-04-01

Synchronous fluorescence spectroscopy was used in combination with principal component analysis (PCA) and linear discriminant analysis (LDA) for the differentiation of plum spirits according to their geographical origin. A total of 14 Czech, 12 Hungarian and 18 Slovak plum spirit samples were used. The samples were divided in two categories: colorless (22 samples) and colored (22 samples). Synchronous fluorescence spectra (SFS) obtained at a wavelength difference of 60 nm provided the best results. Considering the PCA-LDA applied to the SFS of all samples, Czech, Hungarian and Slovak colorless samples were properly classified in both the calibration and prediction sets. 100% of correct classification was also obtained for Czech and Hungarian colored samples. However, one group of Slovak colored samples was classified as belonging to the Hungarian group in the calibration set. Thus, the total correct classifications obtained were 94% and 100% for the calibration and prediction steps, respectively. The results were compared with those obtained using near-infrared (NIR) spectroscopy. Applying PCA-LDA to NIR spectra (5500-6000 cm(-1)), the total correct classifications were 91% and 92% for the calibration and prediction steps, respectively, which were slightly lower than those obtained using SFS. Copyright © 2015 Elsevier Ltd. All rights reserved.

Instructor's guide : - synchronized skating school

OpenAIRE

Mokkila, Eveliina

2011-01-01

The starting point to the Instructor’s guide for synchronized skating school was the situation that Turun Riennon Taitoluistelu figure skating club constantly struggles to get enough skaters to the Beginner team in synchronized skating. The guidebook was written to guide the skating school instructors towards providing more synchronized skating teaching in their lessons. As a result from introducing synchronized skating more in the skating school, it is expected to have more children conti...

Symbol synchronization and sampling frequency synchronization techniques in real-time DDO-OFDM systems

Science.gov (United States)

Chen, Ming; He, Jing; Cao, Zizheng; Tang, Jin; Chen, Lin; Wu, Xian

2014-09-01

In this paper, we propose and experimentally demonstrate a symbol synchronization and sampling frequency synchronization techniques in real-time direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM) system, over 100-km standard single mode fiber (SSMF) using a cost-effective directly modulated distributed feedback (DFB) laser. The experiment results show that the proposed symbol synchronization based on training sequence (TS) has a low complexity and high accuracy even at a sampling frequency offset (SFO) of 5000-ppm. Meanwhile, the proposed pilot-assisted sampling frequency synchronization between digital-to-analog converter (DAC) and analog-to-digital converter (ADC) is capable of estimating SFOs with an accuracy of technique can also compensate SFO effects within a small residual SFO caused by deviation of SFO estimation and low-precision or unstable clock source. The two synchronization techniques are suitable for high-speed DDO-OFDM transmission systems.

NIRS-Based Hyperscanning Reveals Inter-brain Neural Synchronization during Cooperative Jenga Game with Face-to-Face Communication.

Science.gov (United States)

Liu, Ning; Mok, Charis; Witt, Emily E; Pradhan, Anjali H; Chen, Jingyuan E; Reiss, Allan L

2016-01-01

Functional near-infrared spectroscopy (fNIRS) is an increasingly popular technology for studying social cognition. In particular, fNIRS permits simultaneous measurement of hemodynamic activity in two or more individuals interacting in a naturalistic setting. Here, we used fNIRS hyperscanning to study social cognition and communication in human dyads engaged in cooperative and obstructive interaction while they played the game of Jenga™. Novel methods were developed to identify synchronized channels for each dyad and a structural node-based spatial registration approach was utilized for inter-dyad analyses. Strong inter-brain neural synchrony (INS) was observed in the posterior region of the right middle and superior frontal gyrus, in particular Brodmann area 8 (BA8), during cooperative and obstructive interaction. This synchrony was not observed during the parallel game play condition and the dialog section, suggesting that BA8 was involved in goal-oriented social interaction such as complex interactive movements and social decision-making. INS was also observed in the dorsomedial prefrontal cortex (dmPFC), in particular Brodmann 9, during cooperative interaction only. These additional findings suggest that BA9 may be particularly engaged when theory-of-mind (ToM) is required for cooperative social interaction. The new methods described here have the potential to significantly extend fNIRS applications to social cognitive research.

Exploring Meaning Negotiation Patterns in Synchronous Audio and Video Conferencing English Classes in China

Science.gov (United States)

Li, Chenxi; Wu, Ligao; Li, Chen; Tang, Jinlan

2017-01-01

This work-in-progress doctoral research project aims to identify meaning negotiation patterns in synchronous audio and video Computer-Mediated Communication (CMC) environments based on the model of CMC text chat proposed by Smith (2003). The study was conducted in the Institute of Online Education at Beijing Foreign Studies University. Four dyads…

Synchronization of Concurrent Processes

Science.gov (United States)

1975-07-01

Pettersen Stanford Ur.iversity Artificial Intelligence Laboratory ABSTRACT Th oaoer gives an overview of commonly used synchronization primitives and...wr.ters . ut.l.z.ng the DroDo4d synchronization primitive . The solution is simpler and shorter than other known S’ms The first sections of the paper...un reicr»» side il nrcttaary and Identity by block number) Scheduling, process scheduling, synchronization , mutual exclusion, semaphores , critical

The algorithm of random length sequences synthesis for frame synchronization of digital television systems

Directory of Open Access Journals (Sweden)

Аndriy V. Sadchenko

2015-12-01

Full Text Available Digital television systems need to ensure that all digital signals processing operations are performed simultaneously and consistently. Frame synchronization dictated by the need to match phases of transmitter and receiver so that it would be possible to identify the start of a frame. As a frame synchronization signals are often used long length binary sequence with good aperiodic autocorrelation function. Aim: This work is dedicated to the development of the algorithm of random length sequences synthesis. Materials and Methods: The paper provides a comparative analysis of the known sequences, which can be used at present as synchronization ones, revealed their advantages and disadvantages. This work proposes the algorithm for the synthesis of binary synchronization sequences of random length with good autocorrelation properties based on noise generator with a uniform distribution law of probabilities. A "white noise" semiconductor generator is proposed to use as the initial material for the synthesis of binary sequences with desired properties. Results: The statistical analysis of the initial implementations of the "white noise" and synthesized sequences for frame synchronization of digital television is conducted. The comparative analysis of the synthesized sequences with known ones was carried out. The results show the benefits of obtained sequences in compare with known ones. The performed simulations confirm the obtained results. Conclusions: Thus, the search algorithm of binary synchronization sequences with desired autocorrelation properties received. According to this algorithm, the sequence can be longer in length and without length limitations. The received sync sequence can be used for frame synchronization in modern digital communication systems that will increase their efficiency and noise immunity.

Cross-spectrum symbol synchronization

Science.gov (United States)

Mccallister, R. D.; Simon, M. K.

1981-01-01

A popular method of symbol synchronization exploits one aspect of generalized harmonic analysis, normally referred to as the cross-spectrum. Utilizing nonlinear techniques, the input symbol energy is effectively concentrated onto multiples of the symbol clock frequency, facilitating application of conventional phase lock synchronization techniques. A general treatment of the cross-spectrum technique is developed and shown to be applicable across a broad class of symbol modulation formats. An important specific symbol synchronization application is then treated, focusing the general development to provide both insight and quantitative measure of the performance impact associated with variation in these key synchronization parameters: symbol modulation format, symbol transition probability, symbol energy to noise density ratio, and symbol rate to filter bandwidth ratio.

Unidirectional synchronization of Hodgkin-Huxley neurons

Energy Technology Data Exchange (ETDEWEB)

Cornejo-Perez, Octavio [Division de Matematicas Aplicadas y Sistemas, Computacionales, IPICYT, Apdo. Postal 3-74 Tangamanga, 78231 San Luis Potosi (Mexico)]. E-mail: octavio@ipicyt.edu.mx; Femat, Ricardo [Division de Matematicas Aplicadas y Sistemas, Computacionales, IPICYT, Apdo. Postal 3-74 Tangamanga, 78231 San Luis Potosi (Mexico)]. E-mail: rfemat@ipicyt.edu.mx

2005-07-01

Synchronization dynamics of two noiseless Hodgkin-Huxley (HH) neurons under the action of feedback control is studied. The spiking patterns of the action potentials evoked by periodic external modulations attain synchronization states under the feedback action. Numerical simulations for the synchronization dynamics of regular-irregular desynchronized spiking sequences are displayed. The results are discussed in context of generalized synchronization. It is also shown that the HH neurons can be synchronized in face of unmeasured states.

Hybrid synchronization of hyperchaotic Lu system

Indian Academy of Sciences (India)

In this paper, we study the hybrid synchronization between two identical hyperchaotic Lu systems. Hybrid synchronization of hyperchaotic Lu system is achieved through synchronization of two pairs of states and anti-synchronization of the other two pairs of states. Active controls are designed to achieve hybrid ...

A Low-Complexity Joint Synchronization and Detection Algorithm for Single-Band DS-CDMA UWB Communications

DEFF Research Database (Denmark)

Christensen, Lars P.B.

2005-01-01

The problem of asynchronous direct-sequence code division multiple access (DS-CDMA) detection over the ultra-wideband (UWB) multipath channel is considered. A joint synchronization, channel-estimation and multi-user detection scheme based on the adaptive linear minimum mean-square error (LMMSE...

Midterm Stability Evaluation of Wide-area Power System by using Synchronized Phasor Measurements

Science.gov (United States)

Ota, Yutaka; Ukai, Hiroyuki; Nakamura, Koichi; Fujita, Hideki

In recent years, the PMU (Phasor Measurement Unit) receives a great deal of attention as a synchronized measurement system of power systems. Synchronized phasor angles obtained by the PMU provide the effective information for evaluating the stability of a bulk power system. The aspect of instability phenomena during midterm tends to be more complicated, and the stability analysis using the synchronized phasor measurements is significant in order to keep a complicated power system stable. This paper proposes a midterm stability evaluation method of the wide-area power system by using the synchronized phasor measurements. By clustering and aggregating the power system to some coherent groups, the step-out is effectively predicted on the basis of the two-machine equivalent power system model. The midterm stability of a longitudinal power system model of Japanese 60Hz systems constructed by the PSA, which is a hybrid-type power system simulator, is practically evaluated using the proposed method.

Chaos and its synchronization in two-neuron systems with discrete delays

International Nuclear Information System (INIS)

Zhou Shangbo; Liao Xiaofeng; Yu Juebang; Wong Kwokwo

2004-01-01

It is well known that complex dynamic behaviors exist in time-delayed neural systems. Infinite positive Lyapunov exponents can be found in time-delayed chaotic systems since the dimension of such systems is infinite. However, theoretical and experimental models studied thus far are low dimensional systems with only one positive Lyapunov exponent. Consequently, messages masked by such chaotic systems are shown to be easily extracted in some cases. Therefore, communication system with a higher security level can be design by means of the time-delayed neuron systems. In this paper, we firstly investigate the dynamical behaviors of two-neuron systems with discrete delays. Then, the chaos synchronization in time-delayed neuron system is studied based on the method of designing the coupled system and employing Krasovskii-Lyapunov theory to search the synchronization conditions. Numerical results illustrate the correctness of our theoretical analyses

Exponential Synchronization of Networked Chaotic Delayed Neural Network by a Hybrid Event Trigger Scheme.

Science.gov (United States)

Fei, Zhongyang; Guan, Chaoxu; Gao, Huijun; Zhongyang Fei; Chaoxu Guan; Huijun Gao; Fei, Zhongyang; Guan, Chaoxu; Gao, Huijun

2018-06-01

This paper is concerned with the exponential synchronization for master-slave chaotic delayed neural network with event trigger control scheme. The model is established on a network control framework, where both external disturbance and network-induced delay are taken into consideration. The desired aim is to synchronize the master and slave systems with limited communication capacity and network bandwidth. In order to save the network resource, we adopt a hybrid event trigger approach, which not only reduces the data package sending out, but also gets rid of the Zeno phenomenon. By using an appropriate Lyapunov functional, a sufficient criterion for the stability is proposed for the error system with extended ( , , )-dissipativity performance index. Moreover, hybrid event trigger scheme and controller are codesigned for network-based delayed neural network to guarantee the exponential synchronization between the master and slave systems. The effectiveness and potential of the proposed results are demonstrated through a numerical example.

Identical synchronization of nonidentical oscillators: when only birds of different feathers flock together

Science.gov (United States)

Zhang, Yuanzhao; Motter, Adilson E.

2018-01-01

An outstanding problem in the study of networks of heterogeneous dynamical units concerns the development of rigorous methods to probe the stability of synchronous states when the differences between the units are not small. Here, we address this problem by presenting a generalization of the master stability formalism that can be applied to heterogeneous oscillators with large mismatches. Our approach is based on the simultaneous block diagonalization of the matrix terms in the variational equation, and it leads to dimension reduction that simplifies the original equation significantly. This new formalism allows the systematic investigation of scenarios in which the oscillators need to be nonidentical in order to reach an identical state, where all oscillators are completely synchronized. In the case of networks of identically coupled oscillators, this corresponds to breaking the symmetry of the system as a means to preserve the symmetry of the dynamical state— a recently discovered effect termed asymmetry-induced synchronization (AISync). Our framework enables us to identify communication delay as a new and potentially common mechanism giving rise to AISync, which we demonstrate using networks of delay-coupled Stuart-Landau oscillators. The results also have potential implications for control, as they reveal oscillator heterogeneity as an attribute that may be manipulated to enhance the stability of synchronous states.

From information needs to information gathering: a system optimization perspective to ISR synchronization

Science.gov (United States)

Ortiz-Peña, Héctor J.; Nagi, Rakesh; Sudit, Moises; Moskal, Michael D.; Dawson, Michael; Fink, James; Hanratty, Timothy; Heilman, Eric; Tuttle, Daniel

2012-06-01

There has been significant progress recognizing the value of Intelligence, Surveillance, and Reconnaissance (ISR) activities supporting Situational Awareness and Command and Control functions during the past several decades. We consider ISR operations to be proactive (discovering activities or areas of interest), active (activities performed for a particular task that flows down from a hierarchical process) or reactive (critical information gathering due to unexpected events). ISR synchronization includes the analysis and prioritization of information requirements, identification of intelligence gaps and the recommendation of available resources to gather information of interest, for all types of ISR operations. It has become critically important to perform synchronized ISR activities to maximize the efficient utilization of limited resources (both in quantity and capabilities) and, simultaneously, to increase the accuracy and timeliness of the information gain. A study evaluating the existing technologies and processes supporting ISR activities is performed suggesting a rigorous system optimization approach to the ISR synchronization process. Unfortunately, this approach is not used today. The study identifies existing gaps between the current ISR synchronization process and the proposed system optimization approach in the areas of communication and collaboration tools and advanced decision aids (analytics). Solutions are recommended that will help close this gap.

Synchronous adenocarcinomas of the colon presenting as synchronous colocolic intussusceptions in an adult

Directory of Open Access Journals (Sweden)

Chen Chuang-Wei

2012-12-01

Full Text Available Abstract Intussusception is uncommon in adults. To our knowledge, synchronous colocolic intussusceptions have never been reported in the literature. Here we described the case of a 59-year-old female of synchronous colocolic intussusceptions presenting as acute abdomen that was diagnosed by CT preoperatively. Laparotomy with radical right hemicolectomy and sigmoidectomy was undertaken without reduction of the invagination due to a significant risk of associated malignancy. The final diagnosis was synchronous adenocarcinoma of proximal transverse colon and sigmoid colon without lymph nodes or distant metastasis. The patient had an uneventful recovery. The case also emphasizes the importance of thorough exploration during surgery for bowel invagination since synchronous events may occur.

Fault-tolerant clock synchronization in distributed systems

Science.gov (United States)

Ramanathan, Parameswaran; Shin, Kang G.; Butler, Ricky W.

1990-01-01

Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization. The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost overhead imposed by the algorithms. More recent developments such as hardware-assisted software synchronization and algorithms for synchronizing large, partially connected distributed systems are especially emphasized.

Speed Synchronization Control of Integrated Motor–Transmission Powertrain over CAN through Active Period-Scheduling Approach

Directory of Open Access Journals (Sweden)

Wanke Cao

2017-11-01

Full Text Available This paper deals with the speed synchronization control of integrated motor–transmission (IMT powertrain systems in pure electric vehicles (EVs over a controller area network (CAN subject to both network-induced delays and network congestion. A CAN has advantages over point-to-point communication; however, it imposes network-induced delays and network congestion into the control system, which can deteriorate the shifting quality and make system integration difficult. This paper presents a co-design scheme combining active period scheduling and discrete-time slip mode control (SMC to deal with both network-induced delays and network congestion of the CAN, which improves the speed synchronization control for high shifting quality and prevents network congestion for the system’s integration. The results of simulations and hardware-in-loop experiments show the effectiveness of the proposed scheme, which can ensure satisfactory speed synchronization performance while significantly reducing the network’s utilization.

An Autonomous Satellite Time Synchronization System Using Remotely Disciplined VC-OCXOs