40 research outputs found

    Comparison of Performance and Power Consumption Between GPS and Sigfox Positioning Using Pycom Modules

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    Sigfox is one of the newly-emerging LPWAN (Low Power Wide Area Network) technologies aiming to provide power-efficient solutions to the world of IoT. This study presents a comparison between Sigfox Geolocation and GPS (Global Positioning System) in terms of power consumption and performance which includes three metrics: accuracy and precision, response rate and response time. This study includes for the first part a series of lab tests where Sigfox Geolocation and GPS were studied in a single Sleep, Wake up, Idle, Tx/Rx cycle. For the second part, field tests with different geographical parameters (altitude, population, mobility) were conducted. Results of lab tests show that power consumption difference between Sigfox and GPS is a linear function of Idle time. In field tests, GPS presents a far superior performance than Sigfox in all metrics and marginally better power efficiency for relatively short Idle interval. For both GPS and Sigfox, a correlation between power efficiency and performance was observed. Results show that GPS operates best in rural environments while Sigfox stands out in urban ones. Payload size was observed to affect Sigfox in both power consumption and performance while different transmission rates only affect power consumption but do not seem to impact the other metrics. A solution based on the outcome of this study is suggested for a freight-monitoring system where geolocation is handled by GPS and the coordinates transmitted via Sigfox. As an emerging technology under constant development, Sigfox Geolocation is expected to have improved performance in the near future

    Eelgrass detritus as a food source for the sea cucumber Apostichopus japonicus Selenka (Echinidermata: Holothuroidea) in coastal waters of North China: an experimental study in flow-through systems.

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    Eelgrass ecosystems have a wide variety of ecological functions in which living tissues and detritus may be a food source for many marine animals. In this study, we conducted a laboratory simulating experiment to understand the trophic relationship between the eelgrass Zostera marina L and the sea cucumber Apostichopus japonicus. A mixture of decaying eelgrass debris and seafloor surface muddy sediments was used as food to feed A. japonicus, and then specific growth rates (SGR) and fecal production rates (FPR) were measured. According to the proportion of eelgrass debris, we designed five treatment diets, i.e., ES0, ES10, ES20, ES40, and ES100, with eelgrass debris accounting for 0%, 10%, 20%, 40%, and 100% in dry weight, respectively. Results showed that diet composition had a great influence on the growth of A. japonicus. Sea cucumbers could use decaying eelgrass debris as their food source; and when the organic content of a mixture of eelgrass debris and sediment was 19.6% (ES40), a relatively high SGR (1.54%·d(-1)) and FPR (1.31 g·ind.(-1) d(-1)) of A. japonicus were obtained. It is suggested that eelgrass beds can not only provide habitat for the sea cucumber A. japonicus but can also provide an indirect food source for the deposit feeder. This means that the restoration and reconstruction of eelgrass beds, especially in coastal waters of China, would be a potential and effective measure for sea-cucumber fisheries, in respect to both resource restoration and aquaculture of this valuable species

    Sensor Placement Optimization of Visual Sensor Networks for Target Tracking Based on Multi-Objective Constraints

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    With the advancement of sensor technology, distributed processing technology, and wireless communication, Visual Sensor Networks (VSNs) are widely used. However, VSNs also have flaws such as poor data synchronization, limited node resources, and complicated node management. Thus, this paper proposes a sensor placement optimization method to save network resources and facilitate management. First, some necessary models are established, including the sensor model, the space model, the coverage model, and the reconstruction error model, and a dimensionality reduction search method is proposed. Next, following the creation of a multi-objective optimization function to balance reconstruction error and coverage, a clever optimization algorithm that combines the benefits of Genetic Algorithms (GA) and Particle Swarm Optimization (PSO) is applied. Finally, comparison studies validate the methodology presented in this paper, and the combined algorithm can enhance optimization effect while relatively reducing running time. In addition, a sensor coverage method for large-range target space with obstacles is discussed

    Assimilation efficiency (AE) of <i>Apostichopus japonicus</i>.

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    <p>Bars represent standard deviations of the means.</p

    Mean fecal production rates (FPR; g·ind.

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    <p><sup>−<b>1</b></sup><b> d</b><sup>−<b>1</b></sup><b>) of </b><b><i>Apostichopus japonicus</i></b><b> during the experimental period.</b> Means (n = 4) with different letters denoting significant differences (<i>p</i><0.05), and bars representing standard deviations of the means.</p

    Initial and final wet weight (g·ind.<sup>−1</sup>) of <i>A. japonicus</i> for five diet treatments.

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    <p>Note: values with different letters in the same row were significantly different from each other (n = 4, <i>p</i><0.05).</p

    Specific growth rates (SGR; %·d<sup>−1</sup>) of <i>Apostichopus japonicus</i>.

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    <p>Means (n = 4) with different letters denoting significant differences (<i>p</i><0.05), and bars representing standard deviations of the means.</p
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