760,592 research outputs found

    Unified clustering and communication protocol for wireless sensor networks

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    In this paper we present an energy-efficient cross layer protocol for providing application specific reservations in wireless senor networks called the “Unified Clustering and Communication Protocol ” (UCCP). Our modular cross layered framework satisfies three wireless sensor network requirements, namely, the QoS requirement of heterogeneous applications, energy aware clustering and data forwarding by relay sensor nodes. Our unified design approach is motivated by providing an integrated and viable solution for self organization and end-to-end communication is wireless sensor networks. Dynamic QoS based reservation guarantees are provided using a reservation-based TDMA approach. Our novel energy-efficient clustering approach employs a multi-objective optimization technique based on OR (operations research) practices. We adopt a simple hierarchy in which relay nodes forward data messages from cluster head to the sink, thus eliminating the overheads needed to maintain a routing protocol. Simulation results demonstrate that UCCP provides an energy-efficient and scalable solution to meet the application specific QoS demands in resource constrained sensor nodes. Index Terms — wireless sensor networks, unified communication, optimization, clustering and quality of service

    Litter on Wheels: An Ocean Garbage Art Car

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    In the Fall term of 2018, Gettysburg College seniors Bill LeConey and Will Gibson created the world\u27s first Ocean Garbage Art Car, by covering an old Ford truck with plastic bottles (and other trash commonly found in our oceans), to raise awareness about anthropogenic pollution in our seas. Since the 1950’s, plastics have been an essential and ubiquitous commodity in nearly every society on the planet. Plastics find their way into just about every aspect of our lives - from water bottles and cell phone cases, to even advanced medical equipment and space shuttles - it’s no secret how prevalent plastic is. Unfortunately, an overwhelming majority of the ≈450 million tons of plastic produced annually ends up in our oceans, posing a substantial threat to our aquatic life and the ecosystems they reside in. Much of this waste coalesces into gyres called garbage patches - some as large as countries - floating within the water column, and harming the tranquility of the environment they are intruding on. Several environmental art forms similar to our Ocean Garbage Art Car were studied and compared to give a more in depth background on our issue. Many other artists have utilized ocean trash, but ours is a one of a kind. An urgent call to action must take place to cleanup our oceans and to stop the excessive waste of plastic before irreversible repercussions occur. It is our hope that the Ocean Garbage Art Car created in the ES 400 seminar will help raise awareness about this dire issue threatening our planet as we know it

    Analisis Faktor Penyebab Tandan Buah Segar (TBS) Busuk Dan Bahaya Kecelakaan Menggunakan Fishbone Chart (Studi Kasus Pada Bagian Sortasi di PT Sutopo Lestari Jaya)

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    At the PT Sutopo Lestari Jaya sorting work station it was seen that the sorting work environment had an open working environment so that when hot weather operators quickly experienced fatigue and the oil content in FFB would shrink, during the rain the work floor sorting would be slippery caused by FFB oil so makes the operator slip and the loader operator is difficult to drive then FFB quickly decays. So improvements are needed by finding the root cause of the problem experienced by using a fishbone diagram. The results obtained are that the sorting work station needs to be repaired by installing a roof in the sorting work environment. With the roof in the sorting work environment, the company can minimize the losses that occur and can eliminate the causes of problems that exist in the sorting work station

    Flexible dielectric waveguides with powder cores

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    Flexible dielectric waveguides have been demonstrated at 10 GHz and 94 GHz using thin-wall polymer tubing filled with low-loss, high-dielectric-constant powders. Absorptive losses of the order of 10 dB/m were measured at 94 GHz. with nickel-aluminium titanate and barium tetratitanate powder in polytetrafluoroethylene (PTFE) lightweight electrical tubing. Bending losses at 94 GHz were negligible for curvature radii greater than 4 cm. M.H. Kuhn's (1974) theory of three-region cylindrical dielectric waveguide was used to calculate dispersion curves for the lower-order modes for several combinations of dimensions and dielectric constants. Good agreement was obtained between experimental and theoretical values of guide wavelength. A scheme is proposed for classifying hybrid modes of three-region guides based on the ratio |Ez/Hz|. For two-region guides, this reduces to E. Snitzer's (1961) familiar scheme

    Formation of iron sulfide at faecal pellets and other microniches within suboxic surface sediment.

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    Faecal pellet deposition and bioturbation may lead to heterogeneously distributed particles of localized highly reactive organic matter (microniches) being present below the oxygen penetration depth. Where O2, NO3-, and Fe/Mn oxyhydroxides become depleted within these microniches or where they exist in zones of sulfate reduction, significant localized peaks in sulfide concentration can occur. These discrete zones of sulfide evolution can cause formation of iron sulfides that would not be predicted by analysis of the ‘bulk’ sediment. Using a reaction-transport model developed specifically for investigating spherical microniches, and incorporating 3D diffusion, we investigated how the rate constants of organic matter (OM) degradation, particle porosity and niche lifetime, affect dissolved sulfide and iron concentrations, and formation of iron sulfide at such niches. For all of the modelled scenarios the saturation index for iron sulfide is positive, indicating favourable conditions for FeS precipitation in all niches. Those simulations within the microniche lifetime range of 2.5 to 5 days gave comparable concentration ratios of sulfide to iron in solution within the niche to experimentally observed values. Our model results provide insight into the mechanisms of preservation of OM, including soft tissue, in the paleo record, by predicting the conditions that result in preferential deposition of precipitates at the edge of microniches. Decreases in porosity, shorter niche lifetimes and increases in OM degradation rate constants, all tend to increase the likelihood that FeS precipitation will preferentially occur at the edges of a niche, rather than uniformly throughout the niche volume