122,337 research outputs found
Water quality monitoring, control and management (WQMCM) framework using collaborative wireless sensor networks
No full textImproving water quality is of global concern, with agricultural practices being the major contributors to reduced water quality. The reuse of nutrient-rich drainage water can be a valuable strategy to gain economic-environmental benefits. However, currently the tools and techniques to allow this do not exist. Therefore, we have proposed a framework, WQMCM, which utilises increasingly common local farm-scale networks across a catchment, adding provision for collaborative information sharing. Using this framework, individual sub-networks can learn their environment and predict the impact of catchment events on their locality, allowing dynamic decision making for local irrigation strategies. Since resource constraints of network nodes (e.g. power consumption, computing power etc.) require a simplified predictive model for discharges, therefore low-dimensional model parameters are derived from the existing National Resource Conservation Method (NRCS), utilising real-time field values. Evaluation of the predictive models, developed using M5 decision trees, demonstrates accuracy of 84-94% compared with the traditional NRCS curve number model. The discharge volume and response time model was tested to perform with 6% relative root mean square error (RRMSE), even for a small training set of around 100 samples; however the discharge response time model required a minimum of 300 training samples to show reasonable performance with 16% RRMS
A New Macroeconomic Time Series: Business Profitability in Twentieth-Century Australia
No full textMacroeconomic time series, business profitability, Australia
Empirical Evaluation of OI-MAC: Direct Interconnection between Wireless Sensor Networks for Collaborative Monitoring
No full textCooperation between co-located Wireless Sensor Networks (WSNs) has the potential to present new opportunities for novel applications and provide network performance improvements. The traditional interconnection approach for WSNs is based on a backbone network such as the Internet, but this may have intermittent or unavailable connectivity in remote locations. To address this, Opportunistic Direct Interconnection (ODI) has been proposed to allow distinct and independent WSNs to communicate directly with neighbouring networks, and OIMAC is a link-layer protocol which implements this functionality. However, OI-MAC has not been experimentally validated, instead with analysis performed through simulation. In this paper, we present a practical implementation of OI-MAC using two separate multi-hop networks with 6 sensor nodes in each. We validate its effective operation through experimentally obtained timing diagrams, sensor data output, and energy consumption. Results show successful cross-network packet communication, while networks remain independent by maintaining individual configurations and communication channels. Furthermore, we show that the process of discovering neighbouring networks has an insignificant impact on energy consumption
Supercapacitor leakage in energy-harvesting sensor nodes: fact or fiction?
No full textAs interest in energy-harvesting sensor nodes continues to grow, the use of supercapacitors as energy stores or buffers is gaining popularity. The reasons for their use are numerous, and include their high power density, simple interfacing requirements, simpler measurement of state-of-charge, and a greater number of charging cycles than secondary batteries. However, supercapacitor energy densities are orders of magnitude lower. Furthermore, they have been reported to exhibit significant leakage, and this has been shown to increase exponentially with terminal voltage (and hence stored energy). This observation has resulted in a number of algorithms, designs and methods being proposed for effective operation of supercapacitor-based energy-harvesting sensor nodes. In this paper, it is argued that traditional ‘leakage’ is not as significant as has commonly been suggested. Instead, what is observed as leakage is in fact predominantly due to internal charge redistribution. As a result, it is suggested that different approaches are required in order to effectively utilize supercapacitors in energy-harvesting sensor nodes
Merrett (A.J.), Bannock (G.) - Business economics and statistics.
No full textGuitton Henri. Merrett (A.J.), Bannock (G.) - Business economics and statistics.. In: Revue économique, volume 14, n°3, 1963. pp. 476-477
Bathymicrops multispinis Nielsen & Merrett 1992
No full textBathymicrops multispinis Nielsen & Merrett, 1992 – No common name; ③ There are occurrences of B. multispinis off Madeira in the PECS area (Madeira Plain), USNM, No. 344624.5250741, 21.1250º W, 31.2483º N, 20 Aug. 1990; BMNH, No. 1997.1.2.2, 21.1180º W, 31.2358º N. Bathymicrops regis Hjort & Koefoed, 1912Published as part of Carneiro, Miguel, Martins, Rogélia, Landi, Monica & Costa, Filipe O., 2014, Updated checklist of marine fishes (Chordata: Craniata) from Portugal and the proposed extension of the Portuguese continental shelf, pp. 1-73 in European Journal of Taxonomy 73 on page 28, DOI: 10.5852/ejt.2014.73, http://zenodo.org/record/386651
Design of a linearized magnetic spring for body-worn inertial energy harvesters
No full textA potential method for powering body-worn sensors is that of inertial energy harvesting; extracting energy from the movement of the human body. However, the frequencies typically present are <5 Hz, hence requiring physically large devices. A promising solution utilizes a magnetic spring, but these exhibit a non-linear relationship between force (and hence resonant frequency) and displacement. This paper describes a design for implementing a linearized magnetic spring. Finite element analysis is used to model this device and compare against those reported in the literature. Simulation results indicate that, compared to the state-of-the-art, this design exhibits improved linearity (2%) across a wider displacement range (±25 mm). A prototype has been fabricated, and the simulation results experimentally validated
A hidden Markov model-based acoustic cicada detector for crowdsourced smartphone biodiversity monitoring
No full textIn recent years, the field of computational sustainability has striven to apply artificial intelligence techniques to solve ecological and environmental problems. In ecology, a key issue for the safeguarding of our planet is the monitoring of biodiversity. Automated acoustic recognition of species aims to provide a cost-effective method for biodiversity monitoring. This is particularly appealing for detecting endangered animals with a distinctive call, such as the New Forest cicada. To this end, we pursue a crowdsourcing approach, whereby the millions of visitors to the New Forest, where this insect was historically found, will help to monitor its presence by means of a smartphone app that can detect its mating call. Existing research in the field of acoustic insect detection has typically focused upon the classification of recordings collected from fixed field microphones. Such approaches segment a lengthy audio recording into individual segments of insect activity, which are independently classified using cepstral coefficients extracted from the recording as features. This paper reports on a contrasting approach, whereby we use crowdsourcing to collect recordings via a smartphone app, and present an immediate feedback to the users as to whether an insect has been found. Our classification approach does not remove silent parts of the recording via segmentation, but instead uses the temporal patterns throughout each recording to classify the insects present. We show that our approach can successfully discriminate between the call of the New Forest cicada and similar insects found in the New Forest, and is robust to common types of environment noise. A large scale trial deployment of our smartphone app collected over 6000 reports of insect activity from over 1000 users. Despite the cicada not having been rediscovered in the New Forest, the effectiveness of this approach was confirmed for both the detection algorithm, which successfully identified the same cicada through the app in countries where the same species is still present, and of the crowdsourcing methodology, which collected a vast number of recordings and involved thousands of contributors.</p
Energy-Efficient Data Acquisition in Wireless Sensor Networks through Spatial Correlation
No full textThe application of Wireless Sensor Networks (WSNs) is restrained by their often-limited lifetime. A sensor node's lifetime is fundamentally linked to the volume of data that it senses, processes and reports. Spatial correlation between sensor nodes is an inherent phenomenon to WSNs, induced by redundant nodes which report duplicated information. In this paper, we report on the design of a distributed sampling scheme referred to as the 'Virtual Sampling Scheme' (VSS). This scheme is formed from two components: an algorithm for forming virtual clusters, and a distributed sampling method. VSS primarily utilizes redundancy of sensor nodes to get only a subset to sense the environment at any one time. Sensor nodes that are not sensing the environment are in a low-power sleep state, thus conserving energy. Furthermore, VSS balances the energy consumption amongst nodes by using a round robin method
Accurate supercapacitor modeling for energy-harvesting wireless sensor nodes
No full textSupercapacitors are often used in energy-harvesting wireless sensor nodes (EH-WSNs) to store harvested energy. Until now, research into the use of supercapacitors in EH-WSNs has considered them to be ideal or over-simplified, with non-ideal behavior attributed to substantial leakage currents. In this brief, we show that observations previously attributed to leakage are predominantly due to redistribution of charge inside the supercapacitor. We confirm this hypothesis through the development of a circuit-based model which accurately represents non-ideal behavior. The model correlates well with practical validations representing the operation of an EH-WSN, and allows behavior to be simulated over long periods
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