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Communication Channels (communication + channel)
Selected AbstractsExperimental verification of a wireless sensing and control system for structural control using MR dampersEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 10 2007Chin-Hsiung Loh Abstract The performance aspects of a wireless ,active' sensor, including the reliability of the wireless communication channel for real-time data delivery and its application to feedback structural control, are explored in this study. First, the control of magnetorheological (MR) dampers using wireless sensors is examined. Second, the application of the MR-damper to actively control a half-scale three-storey steel building excited at its base by shaking table is studied using a wireless control system assembled from wireless active sensors. With an MR damper installed on each floor (three dampers total), structural responses during seismic excitation are measured by the system's wireless active sensors and wirelessly communicated to each other; upon receipt of response data, the wireless sensor interfaced to each MR damper calculates a desired control action using an LQG controller implemented in the wireless sensor's computational core. In this system, the wireless active sensor is responsible for the reception of response data, determination of optimal control forces, and the issuing of command signals to the MR damper. Various control solutions are formulated in this study and embedded in the wireless control system including centralized and decentralized control algorithms. Copyright © 2007 John Wiley & Sons, Ltd. [source] Improving TCP performance over networks with wireless components using ,probing devices'INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 6 2002A. Lahanas Abstract TCP error control mechanism lacks the ability to detect with precision the nature of potential errors during communication. It is only capable of detecting the results of the errors, namely that segments are dropped. As a result, the protocol lacks the ability to implement an appropriate error recovery strategy cognizant of current network conditions and responsive to the distinctive error characteristics of the communication channel. TCP sender always calls for the sending window to shrink. We show that probing mechanisms could enhance the error detection capabilities of the protocol. TCP could then flexibly adjust its window in a manner that permits the available bandwidth to be exploited without violating the requirements of stability, efficiency and fairness that need to be guaranteed during congestion. Our experiments have three distinct goals: First, to demonstrate the potential contribution of probing mechanisms. A simple probing mechanism and an immediate recovery strategy are grafted into TCP-Tahoe and TCP-Reno. We show that, this way, standard TCP can improve its performance without requiring any further change. Second, to study the performance of adaptive strategies. An adaptive TCP with probing is used, that is responsive to the detected error conditions by alternating slow start, fast recovery and immediate recovery. An adaptive error recovery strategy can yield better performance. Third, to study the design limitations of the probing device itself. The aggressive or conservative nature of the probing mechanisms themselves can determine the aggressive or conservative behaviour of the protocol and exploit accordingly the energy/throughput trade-off. Copyright © 2002 John Wiley & Sons, Ltd. [source] Nonuniform video coding by means of multifoveal geometriesINTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY, Issue 1 2002J.A. Rodríguez This paper presents a control mechanism for video transmission that relies on transmitting nonuniform resolution images depending on the delay of the communication channel. These images are built in an active way to keep the areas of interest of the image at the highest resolution available. In order to shift the areas of high resolution over the image and to achieve a data structure that is easy to process by using conventional algorithms, a shifted foveal multiresolution geometry of adaptive size is used. If delays are too high, the resolution areas of the image can be transmitted at different rates. A functional system has been developed for corridor surveillance with static cameras. Tests with real video images have proven that the method allows an almost constant rate of images per second as long as the channel is not collapsed. A new method for determining the areas of interest is also proposed, based on hierarchical object tracking by means of adaptive stabilization of pyramidal structures. © 2002 John Wiley & Sons, Inc. Int J Imaging Syst Technol 12, 27,34, 2002 [source] A heterogeneous-network aided public-key management scheme for mobile ad hoc networksINTERNATIONAL JOURNAL OF NETWORK MANAGEMENT, Issue 1 2007Yuh-Min Tseng A mobile ad hoc network does not require fixed infrastructure to construct connections among nodes. Due to the particular characteristics of mobile ad hoc networks, most existing secure protocols in wired networks do not meet the security requirements for mobile ad hoc networks. Most secure protocols in mobile ad hoc networks, such as secure routing, key agreement and secure group communication protocols, assume that all nodes must have pre-shared a secret, or pre-obtained public-key certificates before joining the network. However, this assumption has a practical weakness for some emergency applications, because some nodes without pre-obtained certificates will be unable to join the network. In this paper, a heterogeneous-network aided public-key management scheme for mobile ad hoc networks is proposed to remedy this weakness. Several heterogeneous networks (such as satellite, unmanned aerial vehicle, or cellular networks) provide wider service areas and ubiquitous connectivity. We adopt these wide-covered heterogeneous networks to design a secure certificate distribution scheme that allows a mobile node without a pre-obtained certificate to instantly get a certificate using the communication channel constructed by these wide-covered heterogeneous networks. Therefore, this scheme enhances the security infrastructure of public key management for mobile ad hoc networks. Copyright © 2006 John Wiley & Sons, Ltd. [source] Minimal data rate stabilization of nonlinear systems over networks with large delaysINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2010C. De Persis Abstract Control systems over networks with a finite data rate can be conveniently modeled as hybrid (impulsive) systems. For the class of nonlinear systems in feedfoward form, we design a hybrid controller, which guarantees stability, in spite of the measurement noise due to the quantization, and of an arbitrarily large delay, which affects the communication channel. The rate at which feedback packets are transmitted from the sensors to the actuators is shown to be arbitrarily close to the infimal one. Copyright © 2009 John Wiley & Sons, Ltd. [source] Control of Teleoperators with Communication Time Delay through State ConvergenceJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 4 2004Jose M. Azorin This paper describes a new control method of teleoperation systems with communication time delay. This method models the teleoperation system in the state space, considering all the possible interactions that could appear in the operator-master-slave-environment set, and it uses the Taylor expansion to model the time delay. The control system allows that the slave manipulator follows the master in spite of the time delay in the communication channel. The tracking is achieved by state convergence between the master and the slave. The method is also able to establish the desired dynamics of this convergence and the dynamics of the slave manipulator. Furthermore, a simple design procedure is provided to obtain the control system gains. These control gains are calculated solving a set of seven equations. The control method is robust to the uncertainty of the design parameters, so it is not necessary to obtain good estimations of these parameters. Simulations and experiments with a one DOF teleoperation system are presented to verify the control method. © 2004 Wiley Periodicals, Inc. [source] On the connectivity of Bluetooth-based ad hoc networksCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 7 2009P. Crescenzi Abstract We study the connectivity properties of a family of random graphs that closely model the Bluetooth's device discovery process, where each device tries to connect to other devices within its visibility range in order to establish reliable communication channels yielding a connected topology. Specifically, we provide both analytical and experimental evidence that when the visibility range of each node (i.e. device) is limited to a vanishing function of n, the total number of nodes in the system, full connectivity can still be achieved with high probability by letting each node connect only to a ,small' number of visible neighbors. Our results extend previous studies, where connectivity properties were analyzed only for the case of a constant visibility range, and provide evidence that Bluetooth can indeed be used for establishing large ad hoc networks. Copyright © 2008 John Wiley & Sons, Ltd. [source] Ergonomics considerations and management action in the implementation of industrial robotsHUMAN FACTORS AND ERGONOMICS IN MANUFACTURING & SERVICE INDUSTRIES, Issue 3 2001Biman Das To obtain maximum benefit from the implementation of industrial robots, it is necessary to identify specific ergonomics problems and provide answers to such problems. Special features of a typical industrial robot are described. Specific ergonomics problems are identified and discussed: sociopsychological factors, systems safety design, communications, training, and workplace design. For the successful implementation of industrial robots, management should take timely action with regard to advanced planning procedures, user involvement plans, communication channels, company labor policies, and continuous training programs. The technological change from conventional to advanced manufacturing, such as industrial robots, must be jointly supported by all levels of management and workers. © 2001 John Wiley & Sons, Inc. [source] Blind MIMO equalization with optimum delay using independent component analysisINTERNATIONAL JOURNAL OF ADAPTIVE CONTROL AND SIGNAL PROCESSING, Issue 3 2004Vicente Zarzoso Abstract Blind space,time equalization of multiuser time-dispersive digital communication channels consists of recovering the users' simultaneously transmitted data free from the interference caused by each other and the propagation effects, without using training sequences. In scenarios composed of mutually independent non-Gaussian i.i.d. users' signals, independent component analysis (ICA) techniques based on higher-order statistics can be employed to refine the performance of conventional linear detectors, as recently shown in a code division multiple access environment (Signal Process 2002; 82:417,431). This paper extends these results to the more general multi-input multi-output (MIMO) channel model, with the minimum mean square error (MMSE) as conventional equalization criterion. The time diversity introduced by the wideband multipath channel enables a reduction of the computational complexity of the ICA post-processing stage while further improving performance. In addition, the ICA-based detector can be tuned to extract each user's signal at the delay which provides the best MMSE. Experiments in a variety of simulation conditions demonstrate the benefits of ICA-assisted MIMO equalization. Copyright © 2004 John Wiley & Sons, Ltd. [source] Performance analysis of a reuse partitioning technique for multi-channel cellular systems supporting elastic services,INTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 3 2009Gábor Fodor Abstract For multi-cell systems employing intra-cell orthogonal communication channels, inter-cell interference mitigation techniques are expected to be one of the key radio resource management functions. In this paper we propose and analyze a simple reuse partitioning technique (with random and coordinated resource block allocation in neighbor cells) that is able to reduce inter-cell interference. We propose a model that is able to take into account that sessions dynamically enter and leave the system. Rigid sessions require a class-specific fixed number of resource blocks, while elastic sessions can enter the system if a minimum number of resources are allocated to them. In this rather general setting (and using the example of a system employing frequency division for multiple access) we analyze the system performance in terms of the expected number of channel collisions, the session-blocking probabilities, the signal-to-interference-and-noise ratio (SINR) and packet error rate performance. We present numerical results on the various trade-offs between these measures (including the trade-off between the reuse factor and the SINR performance) that provide insight into the behavior of multi-channel cellular systems and help dimensionalize the parameters of a reuse partitioned system. Copyright © 2008 John Wiley & Sons, Ltd. [source] In-building power lines as high-speed communication channels: channel characterization and a test channel ensembleINTERNATIONAL JOURNAL OF COMMUNICATION SYSTEMS, Issue 5 2003Tooraj Esmailian Abstract In-building power lines have often been considered as attractive media for high-speed data transmission, particularly for applications like home networking. In this paper, we develop models for power line channels based both on theoretical considerations and practical measurements. We consider power line channel frequency response and noise models in the 1,30 MHz band and propose a number of power line test channels in which to measure the performance of power line modems. Copyright © 2003 John Wiley & Sons, Ltd. [source] Modularizing inference in large causal probabilistic networksINTERNATIONAL JOURNAL OF INTELLIGENT SYSTEMS, Issue 2 2003Kristian G. Olesen This article describes a number of implementation aspects of modular inference in large medical expert systems based on causal probabilistic networks. Examples are provided from the neuromuscular diagnosting system the muscle and nerve inference network (MUNIN). The inference procedure is outlined and the principal data structure underlying the inference procedure are described. A condensed summary of selected technical details of the inference procedure in causal probabilistic networks (CPNs) is provided. This is required for understanding the implemented modularization of the inference. The modularization of the inference implies a need for transfer of information between modules, which is realized by establishing communication channels between modules. Modules are also used to perform inference by conditioning, a method that reduces storage requirements to a manageable size and thereby prepares the way for MUNINs migration to common PCs. © 2003 Wiley Periodicals, Inc. [source] Maximizing Business Returns to Corporate Social Responsibility (CSR): The Role of CSR CommunicationINTERNATIONAL JOURNAL OF MANAGEMENT REVIEWS, Issue 1 2010Shuili Du By engaging in corporate social responsibility (CSR) activities, companies can not only generate favorable stakeholder attitudes and better support behaviors (e.g. purchase, seeking employment, investing in the company), but also, over the long run, build corporate image, strengthen stakeholder,company relationships, and enhance stakeholders' advocacy behaviors. However, stakeholders' low awareness of and unfavorable attributions towards companies' CSR activities remain critical impediments in companies' attempts to maximize business benefits from their CSR activities, highlighting a need for companies to communicate CSR more effectively to stakeholders. In light of these challenges, a conceptual framework of CSR communication is presented and its different aspects are analyzed, from message content and communication channels to company- and stakeholder-specific factors that influence the effectiveness of CSR communication. [source] Consumer attitudes towards self-referral with early signs of cancer: implications for symptom awareness campaignsINTERNATIONAL JOURNAL OF NONPROFIT & VOLUNTARY SECTOR MARKETING, Issue 4 2007Douglas Eadie Traditionally, secondary prevention programmes have employed mass screening approaches to assess for asymptomatic signs of cancer. It has been suggested that early detection strategies, involving public education and self-referral may prove more cost-effective, with low-risk populations for cancers with symptomatic presentation. The success of public education approaches is dependent on careful consideration of the psycho-social factors of self-examination and referral. This paper presents the findings from an exploratory study, using qualitative methods with an at-risk population of older people living in deprived communities in west-central Scotland. The study examines consumer perceptions of the early detection of cancer and the cultural barriers to self-referral, as well as response to aspects of communication strategy. The implications for design of symptom awareness campaigns, including use of message appeals, specification of target symptoms, identification of target audience and selection of communication channels, are discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Kalman filtering over wireless fading channels,How to handle packet drop,INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 18 2009Yasamin Mostofi Abstract In this paper we consider estimation of dynamical systems over wireless fading communication channels using a Kalman filter. We show the impact of the stochastic communication noise on the estimation process. We furthermore show how noisy packets should be handled in the receiver. More specifically, we illustrate the impact of the availability of a cross-layer information path on the optimum receiver design. In the absence of a cross-layer information path, it was shown that packet drop should be designed to balance information loss and communication noise in order to optimize the performance. In the presence of a cross-layer path, we show that keeping all the packets will minimize the average estimation error covariance. We also derive the stability condition in the presence of noisy packets and show that it is independent of the shape of the communication noise variance or availability of a cross-layer information path. Copyright © 2008 John Wiley & Sons, Ltd. [source] Design of distributed controllers with constrained and noisy linksINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 18 2006Shengxiang Jiang Abstract In this paper we consider some design aspects of distributed controllers that guarantee a ,, performance level. In particular, we consider two design problems. First, is the case where, without loss of generality, there are two distributed subcontrollers connected to a (generalized) plant and the interest is placed in minimizing the number of noise-free (and dynamics free) communication channels between the subcontrollers needed to provide a given performance. The second is the case where, given a distributed controller designed in the first case, communication noise is present and we seek an optimal choice of the communication signals to guarantee a performance level while keeping the communication signal to noise power limited. We take a linear matrix inequality (LMI) approach to provide solution procedures to these problems and present examples that demonstrate their efficiency. Copyright © 2006 John Wiley & Sons, Ltd. [source] Continuing Medical Education, Continuing Professional Development, and Knowledge Translation: Improving Care of Older Patients by Practicing PhysiciansJOURNAL OF AMERICAN GERIATRICS SOCIETY, Issue 10 2006David C. Thomas MD Many community-based internists and family physicians lack familiarity with geriatrics knowledge and best practices, but they face overwhelming fiscal and time barriers to expanding their skills and improving their behavior in the care of older people. Traditional lecture-and-slide-show continuing medical education (CME) programs have been shown to be relatively ineffective in changing this target group's practice. The challenge for geriatrics educators, then, is to devise CME programs that are highly accessible to practicing physicians, that will have an immediate and significant effect on practitioners' behavior, and that are financially viable. Studies of CME have shown that the most effective programs for knowledge translation in these circumstances involve what is known as active-mode learning, which relies on interactive, targeted, and multifaceted techniques. A systematic literature review, supplemented by structured interviews, was performed to inventory active-mode learning techniques for geriatrics knowledge and skills in the United States. Thirteen published articles met the criteria, and leaders of 28 active-mode CME programs were interviewed. This systematic review indicates that there is a substantial experience in geriatrics training for community-based physicians, much of which is unpublished and incompletely evaluated. It appears that the most effective methods to change behaviors involved multiple educational efforts such as written materials or toolkits combined with feedback and strong communication channels between instructors and learners. [source] The Role of Trust in Channels of Strategic Communication for Building Civil SocietyJOURNAL OF COMMUNICATION, Issue 4 2005Carl H. Botan In these turbulent times, development communication is a growing and important area of both academic research and practice. This article explores the role of strategic communication channels in the development of civil society in Bosnia. This case study reports the results of a survey that asked Bosnians about their levels of trust in government officials, alternative media, and state-controlled media outlets. The findings suggest that shortly after the war Bosnians had medium levels of trust in their communication channels, and when it comes to obtaining important information, it appears that alternative media were considered more trustworthy than either the state media or local government officials. Finally, political affiliation and ethnicity affect trust in communication channels in complex ways. [source] Decision process support for participatory democracyJOURNAL OF MULTI CRITERIA DECISION ANALYSIS, Issue 1-2 2008Mats Danielson Abstract This paper presents a project and case study integrating decision methods into democratic processes. The case discussed is a set of three complicated decisions in a municipality in Sweden. The decisions had been postponed on several occasions prior to bringing in the method described in the paper. The method employed consists of two main parts. The interaction part contains the communication channels directed to the stakeholders. The decision-process part consists of a three-layered working process model. As a part of the method, the project was highly visible on the web. Citizens were encouraged to submit material to the project. All intermediate results of the process were continuously published, enhancing transparency. For each decision, the analysis consisted of comparing all alternatives, taking the respective criteria into account as weighted or ranked by the participants. A method for recording compromises analytically was also used. The purpose was not to replace the political process but to support it in a structured way. Copyright © 2007 John Wiley & Sons, Ltd. [source] Vital signs for vital people: an exploratory study into the role of the Healthcare Assistant in recognising, recording and responding to the acutely ill patient in the general ward settingJOURNAL OF NURSING MANAGEMENT, Issue 5 2010JAYNE JAMES RN., Ortho. james j., butler-williams c., hunt j. & cox h. (2010) Journal of Nursing Management18, 548,555 Vital signs for vital people: an exploratory study into the role of the Healthcare Assistant in recognising, recording and responding to the acutely ill patient in the general ward setting Aim, To examine the contribution of the Healthcare Assistant (HCA) as the recogniser, responder and recorder of acutely ill patients within the general ward setting. Background, Concerns have been highlighted regarding the recognition and management of the acutely ill patient within the general ward setting. The contribution of the HCA role to this process has been given limited attention. Methods, A postal survey of HCAs was piloted and conducted within two district general hospitals. Open and closed questions were used. Results, Results suggest that on a regular basis HCAs are caring for acutely ill patients. Contextual issues and inaccuracies in some aspects of patient assessment were highlighted. It would appear normal communication channels and hierarchies were bypassed when patients' safety was of concern. Educational needs were identified including scenario-based learning and the importance of ensuring mandatory training is current. Conclusions and implications for nursing management, HCAs play a significant role in the detection and monitoring of acutely ill patients. Acknowledgement is needed of the contextual factors in the general ward setting which may influence the quality of this process. The educational needs identified by this study can assist managers to improve clinical supervision and educational input in order to improve the quality of care for acutely ill patients. [source] Assessing online issue threats: issue contagions and their effect on issue prioritisationJOURNAL OF PUBLIC AFFAIRS, Issue 4 2002W. Timothy Coombs Abstract To be effective, issue managers must develop a sophisticated understanding of the Internet's effect on issues management. Our current understanding is in an early phase of description. We know that the Internet makes it easier for publics to form so they can press an issue but precious little is known of how the dynamic operates. The issue contagion perspective is offered as an explanatory and prescriptive device. The idea of an issue contagion posits that the Internet provides a means for altering issue priorities, often with blinding speed. One route for change is altering the likelihood; a common evaluative tool for prioritising issues that assesses the probability of an issue gaining strength and requiring action. Through various Internet communication channels, attempts can be made to change the likelihood of an issue requiring attention and action , an issue manager will witness shifts in issue prioritisation. This paper details why likelihood is important, how it can be altered via the Internet, and the implications for issue managers. Copyright © 2002 Henry Stewart Publications. [source] State digital library usability: Contributing organizational factorsJOURNAL OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE AND TECHNOLOGY, Issue 13 2002Hong (Iris) Xie Usage and user feedback about a state digital library, in which the developers/designers, content providers, different types of libraries and their staffs, and a variety of user groups represent a loose federation of separate organizations with diverse expectations and needs, are investigated. Through corroboratory evidence from usage statistics of Internet-based database services available through the digital library, responses to a statewide-administered library survey, and a Web-based survey of end users, the authors identify contributing factors for the organizational usability of state digital libraries. The authors refine and enhance an organizational usability model for the unique environment of state digital libraries and identify three modes of interaction (influence, communication, activity) and the challenges each interaction presents: in addressing diverse player needs and expectations; the unequal awareness and training in using state digital libraries; and the lack of sufficient communication channels among players. In addition, the findings highlight the double-edged impact of physical libraries on the state digital library. [source] Lighting up gap junction channels in a flashBIOESSAYS, Issue 10 2002W. Howard Evans Gap junction intercellular communication channels permit the exchange of small regulatory molecules and ions between neighbouring cells and coordinate cellular activity in diverse tissue and organ systems. These channels have short half-lives and complex assembly and degradation pathways. Much of the recent work elucidating gap junction biogenesis has featured the use of connexins (Cx), the constituent proteins of gap junctions, tagged with reporter proteins such as Green Fluorescent Protein (GFP) and has illuminated the dynamics of channel assembly in live cells by high-resolution time-lapse microscopy. With some studies, however, there are potential short-comings associated with the GFP chimeric protein technologies. A recent report by Gaietta et al., has highlighted the use of recombinant proteins with tetracysteine tags attached to the carboxyl terminus of Cx43, which differentially labels ,old' and ,new' connexins thus opening up new avenues for studying temporal and spatial localisation of proteins and in situ trafficking events.1 BioEssays 24:876,880, 2002. © 2002 Wiley Periodicals, Inc. [source] | |||||||||||||||||||