The Effect of Members' Satisfaction with a Virtual Community on Member Participation

The authors develop a four-dimensional scale to measure members'satisfaction with virtual communities. The dimensions consist ofmembers' satisfaction with member-member interactions,organizer-member interactions, organizer-community interactions, andthe community's site. Using a sample of 3605 members of a virtualcommunity the authors investigate the effect of each satisfactiondimension on member participation and the moderating effect ofmembership length on the links between the satisfaction dimensions andmember particip ation. The results reveal that satisfaction withmember-member interactions, organizer-member interactions and thecommunity's site have positive effects on member participation.Satisfaction with organizer-community interactions has no effect onmember participation. The findings also show that the linkages betweenthe satisfaction dimensions and member participation are moderated bymembership length.satisfaction;internet;virtual community;consumers;relationship age

Social control in online communities of consumption: a framework for community management

Online communities of consumption (OCCs) represent highly diverse groups of consumers whose interests are not always aligned. Social control in OCCs aims to effectively manage problems arising from this heterogeneity. Extant literature on social control in OCCs is fragmented as some studies focus on the principles of social control, while others focus on the implementation. Moreover, the domain is undertheorized. This article integrates the disparate literature on social control in OCCs providing a first unified conceptualization of the topic. The authors conceptualize social control as a system, or configuration, of moderation practices. Moderation practices are executed during interactions operating under different governance structures (market, hierarchy, and clan) and serving different purposes (interaction initiation, maintenance, and termination). From this conceptualization, important areas of future research emerge and research questions are developed. The framework also serves as a community management tool for OCC managers, enabling the diagnosis of social control problems and the elaboration of strategies and tactics to address them

Exploiting programmable architectures for WiFi/ZigBee inter-technology cooperation

The increasing complexity of wireless standards has shown that protocols cannot be designed once for all possible deployments, especially when unpredictable and mutating interference situations are present due to the coexistence of heterogeneous technologies. As such, flexibility and (re)programmability of wireless devices is crucial in the emerging scenarios of technology proliferation and unpredictable interference conditions. In this paper, we focus on the possibility to improve coexistence performance of WiFi and ZigBee networks by exploiting novel programmable architectures of wireless devices able to support run-time modifications of medium access operations. Differently from software-defined radio (SDR) platforms, in which every function is programmed from scratch, our programmable architectures are based on a clear decoupling between elementary commands (hard-coded into the devices) and programmable protocol logic (injected into the devices) according to which the commands execution is scheduled. Our contribution is two-fold: first, we designed and implemented a cross-technology time division multiple access (TDMA) scheme devised to provide a global synchronization signal and allocate alternating channel intervals to WiFi and ZigBee programmable nodes; second, we used the OMF control framework to define an interference detection and adaptation strategy that in principle could work in independent and autonomous networks. Experimental results prove the benefits of the envisioned solution

Modelling and analysis of asymmetrical latency in packet-based networks for current differential protection application

Current differential protection typically requires symmetrical communications channels—with equal latency in each direction—for correct operation. Conventionally, this has been delivered using protocols such as IEEE C37.94 over a Time-Division Multiplexing (TDM) wide-area network (WAN). Modern packet-based WANs offer improvements in efficiency, flexibility, and cost-effectiveness for utility applications. However, jitter is unavoidable in packet-based networks and, in extreme cases, jitter inevitably results in substantial asymmetrical latency in communications paths. This paper clearly defines how a new source of asymmetry arises due to the use of "de-jitter" buffers, which can jeopardize critical protection services. This is demonstrated using an analytical modelling approach, which precisely quantifies the degree of risk, and through real-time demonstration with actual devices, involving current differential protection over an IP/MPLS WAN. Using a novel method of real-time manipulation of Ethernet traffic to emulate large WANs, the modelling approach has been validated. It is shown how the sensitivity of relays to asymmetry depends on the protection settings and the magnitude of the measured load current. To address the risk of protection maloperation, a new approach for compensating for asymmetrical latency has been comprehensively validated. These developments will be of immediate interest to utilities operating, or migrating to, a packet-based infrastructure

Validating secure and reliable IP/MPLS communications for current differential protection

Current differential protection has stringent real-time communications requirements and it is critical that protection traffic is transmitted securely, i.e., by using appropriate data authentication and encryption methods. This paper demonstrates that real-time encryption of protection traffic in IP/MPLS-based communications networks is possible with negligible impact on performance and system operation. It is also shown how the impact of jitter and asymmetrical delay in real communications networks can be eliminated. These results will provide confidence to power utilities that modern IP/MPLS infrastructure can securely and reliably cater for even the most demanding applications

Micro-X-Ray Fluorescence and the Old Masters: Non-destructive in situ characterisation of the varnish of historical Low Countries stringed musical instruments

In recent years, a growing attention has been addressed to the study of the varnish from early musical instruments. The surfaces of nine historical Low Countries stringed musical instruments from the collection of the "Musical Instruments Museum” in Brussels were non-destructively analysed by in situ micro-X-Ray Fluorescence spectroscopy in dispersive mode. It was found that the main pigments dispersed in the varnish were iron- and manganese-based earths. The presence of a chromium-based pigment in one of the analysed instruments makes it appreciably different from the others. Other findings were discussed and compared with previously published results. The collection of such information plays a relevant role in the recovery of the applied formulations that is an interesting issue for conservators, luthiers and art historian

Virtuele communities voorbij de hype: Nieuw inzichten voor managers, marketeers en marktonderzoekers

Consumenten leggen steeds vaker contact met elkaar via het Internet. Elektronische discussieforums, mededelingenborden, nieuwsgroepen, e-maillijsten, chatrooms en weblogs bieden consumenten, waar dan ook ter wereld, de mogelijkheid om hun kennis, ervaringen en meningen te delen. De populariteit van deze elektronische contacten tussen consumenten blijkt uit de grote hoeveelheid virtuele communities die georganiseerd zijn rondom consumptiegerelateerde interesses. Dit soort communities vertegenwoordigen uitgebreide netwerken van consumptiekennis en kameraadschap die invloed hebben op consumentengedrag. In dit artikel gaan we in op een aantal nieuwe inzichten ten aanzien van virtuele communities die managers, marketeers en marktonderzoekers beter in staat stellen om strategisch gebruik te maken van de vele mogelijkheden die nu nog vaak onbenut worden gelaten

A novel design of autonomously healed concrete : towards a vascular healing network

Concrete is prone to crack formation in the tensile zone, which is why steel reinforcement is introduced in these zones. However, small cracks could still arise, which give liquids and gasses access to the reinforcement causing it to corrode. Self-healing concrete repairs and seals these small (300 µm) cracks, preventing the development of corrosion. In this study, a vascular system, carrying the healing agent, is developed. It consists of tubes connected to a 3D printed distribution piece. This distribution piece has four outlets that are connected to the tubes and has one inlet, which is accessible from outside. Several materials were considered for the tubes, i.e., polymethylmethacrylate, starch, inorganic phosphate cement and alumina. Three-point-bending and four-point-bending tests proved that self-healing and multiple self-healing is possible with this developed vascular system