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The digital world offers ample availability of data, both historic and real-time. While this capability has the potential for better decision making, the contrary can be the case for a human actuator. Information overflow causes mental overload rather than empowerment of choice. In the context of traditional supermarket shopping, for example, customers are exposed to unstructured and complex product information including ingredients, nutrition facts, product labels, and more. Processing all this information in the context of multiple sustainability aspects requires expert knowledge. On the other hand, the rise of digitalization and the Internet of Things can be used to assist and empower customers during this shopping process. However, an integrated solution is required to provide a high grade of usability and crucial complexity reduction for customers. Therefore, we outline an IoT decision support system that assists customers on the sales floor and enables better decision making according to personal preferences and sustainable consumption. It integrates an indoor localization system, a product information database, and a ranking system considering the individual shopping preferences, where the latter is specified by the customer within an interactive smartphone application. The discussed IoT decision support system was deployed and tested in two retail stores. Its interaction with non-expert test participants was observed over months, and the results are summarized in this contribution.

The theory of pulse-coupled oscillators provides a framework to formulate and develop self-organizing synchronization strategies for wireless communications and mobile computing. These strategies show low complexity and are adaptive to changes in the network. Even though several protocols have been proposed and theoretical insight was gained there is no proof that guarantees synchronization of the oscillator phases in general dynamic coupling topologies under technological constraints. Here, we introduce a family of coupling strategies for pulse-coupled oscillators and prove that synchronization emerges for systems with arbitrary connected and dynamic topologies, individually changing signal propagation and processing delays, and stochastic pulse emission. It is shown by simulations how unreliable links or intentionally incomplete communication between oscillators can improve synchronization performance.

In this paper we present a novel method for detecting wear in a ball screw. A ball screw is a linear actuator that translates rotational motion to linear motion or vice versa. Monitoring ball screws in a timely manner is important to ensure availability of machines and therefore productivity. The method is developed in a data-driven approach by analyzing annotated measurement data of different ball screws from different manufacturers and identifying the significant differences between good and worn ball screws. This produces three meaningful indicators for wear, related to failure modes. One of the indicators is obtained via vibration analysis. Signals from an accelerometer are transformed to frequency space by fast Fourier transformation, and certain frequency bands are observed for abnormalities like a permanently increased spectral energy. Another indicator is obtained by observing the temperature of the spindle, which is affected by higher internal friction due to the damage. Increased friction also affects efficiency of a ball screw. Hence, the engine that drives a ball screw has to deliver more power to produce the same output power. Each of these three indicators delivers a characteristic value related to the fault state of a ball screw. Long term test measurements at different ball screws show the capability of the method.

In industrial applications of wireless sensor networks (WSNs), synchronized sampling of data on each sensor node is often required. Thus, the wireless communication protocol needs to support accurate timing synchronization. If due to a high sampling rate also high data throughput is required, WSNs based on the IEEE 802.15.4 physical layer often do not provide sufficient data rate. Wireless communications based on the well-established IEEE 802.11 wireless local area network (WLAN) standard provides high data throughput but not an accurate timing synchronization unless the protocol stack is severely changed. We propose two low-complexity consensus-based synchronization algorithms for the hybrid WSN introduced, which are executable at limited embedded computing capacity, e.g., on an 8-b microcontroller. A time division multiple access-based synchronization packet broadcasting with three-step-controlled or proportional-integral (PI)-controlled clock adjustment enables 1-kHz sensor sampling rate with a sampling jitter $\mu $ s for the three-step-controlled synchronization algorithm and $ for the PI-controlled algorithm.

International Journal of Distributed Systems and Technologies, 8 (4), ISSN:1947-3532, ISSN:1947-3540

Solutions for time synchronization based on coupled oscillators operate in a self-organizing and adaptive manner and can be applied to various types of dynamic networks. The basic idea was inspired by swarms of fireflies, whose flashing dynamics shows an emergent behavior. This article introduces such a synchronization technique whose main components are “inhibitory coupling” and “self-adjustment.” Based on this new technique, a number of contributions are made. First, we prove that inhibitory coupling can lead to perfect synchrony independent of initial conditions for delay-free environments and homogeneous oscillators. Second, relaxing the assumptions to systems with delays and different phase rates, we prove that such systems synchronize up to a certain precision bound. We derive this bound assuming inhomogeneous delays and show by simulations that it gives a good estimate in strongly-coupled systems. Third, we show that inhibitory coupling with self-adjustment quickly leads to synchrony with a precision comparable to that of excitatory coupling. Fourth, we analyze the robustness against faulty members performing incorrect coupling. While the specific precision-loss encountered by such disturbances depends on system parameters, the system always regains synchrony for the investigated scenarios.

A distributed synchronization protocol based on the theory of pulse-coupled oscillators and timestamps is proposed, implemented on IEEE 802.15.4 compatible Z1 devices, and evaluated in a multihop wireless sensor network. The protocol is robust against the stochastic nature of the wireless channel and provides compensations against random delays. Results show convergence within a few cycles to a synchronization precision of a few hundred microseconds without casting off the control overhead. The performance is compared to that of the standard implementation of the Flooding Time Synchronization Protocol (FTSP).

Solutions for time synchronization based on coupled oscillators operate in a self-organizing and adaptive manner and can be applied to various types of dynamic networks. In this demo, we present the actual implementation of our guaranteed self-organizing synchronization algorithm on packet based networks like wireless sensor networks as well as on iPhone devices (by using acoustic signals). The algorithm is purposed for pulse couple oscillators and exploits the interactions between them to guarantee synchronization on arbitrary network topologies. It supports the design of scalable, minimal control toter and energy efficient communication protocols for fully distributed synchronization.

In a system of pulse-coupled oscillators with delays, inhibitory coupling assures synchronization and convergence if the oscillators are fully connected. This paper investigates inhibitory coupling in non-fully-connected networks by means of simulation. First, we show that an existing inhibitory coupling scheme does not perform well in random networks. Second, we propose a simple modification, which tends to improve the synchronizing behavior of inhibitory coupling.

In performance evaluations of communication and computer networks the underlying topology is sometimes modeled as a random graph. To avoid unwanted side effects, some researchers force the simulated topologies to be connected. Consequently, the resulting distribution of the node degrees does then no longer correspond to that of the underlying random graph model. Being not aware of this change in the degree distribution might result in a simulation pitfall. This paper addresses the question as to how serious this pitfall might be. We analyze the node degree distribution in connected random networks, deriving an approximation for large networks and an upper bound for networks of arbitrary order. The tightness of these expressions is evaluated by simulation. The analysis of the distribution for large networks is extended to k-connected graphs. Results show that specific restricted binomial distributions match the actual degree distribution better than the random graph degree distribution does. Nevertheless, the pitfall of not being aware of the change in the distribution seems not to be a serious mistake in typical setups with large networks.

We analyze global synchronization of oscillator networks with inhibitory delayed and non-delayed pulse coupling. For a fully-coupled system without delays, we propose simple modifications to the state-of-the-art. We prove that the resulting system converges to full in-phase synchronization of all oscillators from arbitrary initial conditions. For systems with arbitrarily distributed delays we propose a second, related approach. We prove that here a state close to synchrony is globally and asymptotically stable, such that all oscillators lock up to a certain precision from arbitrary initial conditions. The precision of synchronization is determined by the coupling strength and the maximal delay appearing.

We design the interactions between oscillators communicating via variably delayed pulse coupling to guarantee their synchronization on arbitrary network topologies. We identify a class of response functions and prove convergence to network-wide synchrony from arbitrary initial conditions. Synchrony is achieved if the pulse emission is unreliable or intentionally probabilistic. These results support the design of scalable, reliable and energy- efficient communication protocols for fully distributed synchronization as needed, e.g., in mobile phone networks, embedded systems, sensor networks and autonomously interacting swarm robots.

We are living in a world of vast information. The means of the Internet allow access to diverse sources of information, with social media and Internet of Things technologies significantly expanding the informational ecosystem. With the use of social media it is easy for ‘like-minded’ people to group up and initiate movements. One way to articulate such movements is via political consumerism. Users group together and boycot or buycot (boost purchases) for certain products with a concrete collective goal in mind. If however the collective goal is vague and abstract, as in the case of sustainability, this bottom-up strategy may loose its popularity and attraction. In this paper we introduce a new concept of how individual consumers can follow their own understanding of sustainability, while at the same time benefiting from collective and participatory actions. We discuss how the means of ICT can be used to develop political consumerism further to transform individual policies into collective statements. &nbsp