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En este documento, proponemos una solución de eficiencia energética para implementar la codificación de red (NC) en redes inalámbricas basada en el estándar IEEE 802.11. El mecanismo propuesto, llamado GreenCode, permite a los nodos realizar el ciclo de trabajo cambiando a un estado de baja potencia (suspensión) cuando escuchan transmisiones de paquetes codificados que no proporcionarán ninguna información nueva para ellos. Para facilitar la operación de suspensión, las transmisiones bidireccionales que involucran paquetes codificados y no codificados entre pares de nodos remitente-receptor se integran en la operación de GreenCode. Tanto los resultados analíticos como de simulación presentados en este documento muestran la alta eficiencia energética de GreenCode con ganancias de hasta el 360% en comparación con los mecanismos existentes basados en el Estándar IEEE 802.11. Dans cet article, nous proposons une solution écoénergétique pour la mise en œuvre du codage de réseau (NC) dans les réseaux sans fil basée sur la norme IEEE 802.11. Le mécanisme proposé, appelé GreenCode, permet aux nœuds de fonctionner en passant à un état de faible puissance (veille) lorsqu'ils entendent des transmissions de paquets codés qui ne leur fourniront aucune nouvelle information. Pour faciliter le fonctionnement en veille, des transmissions bidirectionnelles impliquant à la fois des paquets codés et non codés entre des paires de nœuds expéditeurs-récepteurs sont intégrées dans le fonctionnement de GreenCode. Les résultats d'analyse et de simulation présentés dans cet article montrent l'efficacité énergétique élevée de GreenCode avec des gains allant jusqu'à 360% par rapport aux mécanismes existants basés sur la norme IEEE 802.11. In this paper, we propose an energy-efficient solution for implementing Network Coding (NC) in wireless networks based on the IEEE 802.11 Standard. The proposed mechanism, called GreenCode, allows nodes to duty cycle by switching to a low-power (sleep) state when they overhear coded packet transmissions that will not provide any new information for them. To facilitate the sleep operation, bidirectional transmissions involving both coded and non-coded packets between pairs of sender-receiver nodes are integrated into the operation of GreenCode. Both analytical and simulation results presented in this paper show the high energy efficiency of GreenCode with gains of up to 360% when compared to the existing mechanisms based on the IEEE 802.11 Standard. في هذه الورقة، نقترح حلاً موفرًا للطاقة لتنفيذ ترميز الشبكة (NC) في الشبكات اللاسلكية بناءً على معيار IEEE 802.11. تسمح الآلية المقترحة، المسماة GreenCode، للعقد بدورة العمل عن طريق التبديل إلى حالة منخفضة الطاقة (السكون) عندما تسمع عمليات إرسال الحزم المشفرة التي لن توفر أي معلومات جديدة لها. لتسهيل عملية السكون، يتم دمج عمليات الإرسال ثنائية الاتجاه التي تنطوي على كل من الحزم المشفرة وغير المشفرة بين أزواج من عقد المرسل والمستقبل في تشغيل GreenCode. تُظهر كل من النتائج التحليلية والمحاكاة المقدمة في هذه الورقة كفاءة الطاقة العالية للـ GreenCode مع مكاسب تصل إلى 360 ٪ بالمقارنة مع الآليات الحالية القائمة على معيار IEEE 802.11.

AbstractThis work reports the synthesis, characterization, photophysical, and photovoltaic properties of five new thieno[3,2‐b][1]benzothiophene isoindigo (TBTI)‐containing low bandgap donor–acceptor conjugated polymers with a series of comonomers and different side chains. When TBTI is combined with different electron‐rich moieties, even small structural variations can have significant impact on thin film morphology of the polymer:phenyl C70 butyric acid methyl ester (PCBM) blends. More importantly, high‐resolution electron energy loss spectroscopy is used to investigate the phase‐separated bulk heterojunction domains, which can be accurately and precisely resolved, enabling an enhanced correlation between polymer chemical structure, photovoltaic device performance, and morphology.

A central concern for large-scale sensor networks and the Internet of Things (IoT) has been battery capacity and how to recharge it. Recent advances have pointed to a technique capable of collecting energy from radio frequency (RF) waves called radio frequency-based energy harvesting (RF-EH) as a solution for low-power networks where cables or even changing the battery is unfeasible. The technical literature addresses energy harvesting techniques as an isolated block by dealing with energy harvesting apart from the other aspects inherent to the transmitter and receiver. Thus, the energy spent on data transmission cannot be used together to charge the battery and decode information. As an extension to them, we propose here a method that enables the information to be recovered from the battery charge by designing a sensor network operating with a semanticfunctional communication framework. Moreover, we propose an event-driven sensor network in which batteries are recharged by applying the technique RF-EH. In order to evaluate system performance, we investigated event signaling, event detection, empty battery, and signaling success rates, as well as the Age of Information (AoI). We discuss how the main parameters are related to the system behavior based on a representative case study, also discussing the battery charge behavior. Numerical results corroborate the effectiveness of the proposed system.

Wind turbine gearbox operates under a wide array of highly fluctuating and dynamic load conditions caused by the stochastic nature of wind and operational wind turbine controls. Micropitting damage is one of failure modes commonly observed in wind turbine gearboxes. This article investigates gear micropitting of high-speed stage gears of a wind turbine gearbox operating under nominal and varying load and speed conditions. Based on the ISO standard of gear micropitting (ISO/TR 15144-1:2010) and considering the operating load and speed conditions, a theoretical study is carried out to assess the risk of gear micropitting by determining the contact stress, sliding parameter, local contact temperature and lubricant film thickness along the line of action of gear tooth contact. The non-uniform distributions of temperature and lubricant film thickness over the tooth flank are observed due to the conditions of torque and rotational speed variations and sliding contact along the gear tooth flanks. The lubricant film thickness varies along the tooth flank and is at the lowest when the tip of the driving gear engages with the root of the driven gear. The lubricant film thickness increases with the increase of rotational speed and decreases as torque and sliding increase. It can be concluded that micropitting is most likely to initiate at the addendum of driving gear and the dedendum of driven gear. The lowest film thickness occurs when the torque is high and the rotational speed is at the lowest which may cause direct tooth surface contact. At the low-torque condition, the varying rotational speed condition may cause a considerable variation of lubricant film thickness thus interrupting the lubrication which may result in micropitting.

This article examines the porosity of national borders using the examples of two nuclear facilities at Gorleben and Morsleben located at the West German municipality in the state of Lower Saxony as well as the former Börde district of Saxony-Anhalt (former East Germany). Gorleben and Morsleben became known for their final nuclear waste repositories located directly at the German-German border. Debates and protests surrounding the facilities began in the 1970s and continued after the wall came down. Since opponents had to deal with two different political systems, protests differed in their duration, effect, and methods, even though the border as such was not the problem since West Germans were allowed into the GDR. Transboundary relations were much rather limited by the dictatorial regime on the one side, by the absence of anti-nuclear groups in the GDR until the mid-1980s, and by sufficient coalition partners for West German activists in their own country. Since the disclosure of environmental data by the East German government and the Chernobyl accident a few years later, transboundary relations increased and activists interconnected in many ways. With their protest they indicated that even if the border was a fact, concerns of people in both states transcended it and that borderlands are often characterized by relationality and entanglement.

Combining electrochemical and biological catalysis creates more suitable and efficient routes for the processing of renewable resources, such as CO2 and biomass.

Long tubes with small internal diameter find increasing applications in indirect concentrated solar receivers using an Upflow Bubbling Fluidized Bed of Geldart-A powders as heat carrier. Although successfully demonstrated for tubes of 0.5 to 1 m length, longer tubes are required to increase the solar energy capture efficiency and capacity. The fluidization phenomena differ with the tube length, and freely bubbling fluidization will be transformed into slugging, thus hampering the heat transfer. The behavior of Geldart-A powders in tall tubes of small I.D. has not been extensively studied. The research experimentally investigated the different fluidization modes in a 4 m long tube, and demonstrated the occurrence of freely bubbling at the bottom section of the bed, and slugging from a bed depth in excess of about 1.25 m. Slug characteristics (frequency, length, velocity) were measured and correlated. The results were used to validate 3D numerical simulations based on an Euler-Euler approach in the NEPTUNE_CFD code applied to a fine mesh of 15,000,000 cells. A positive match between experimental and simulation results concerning frequency and velocity of large bubble structures was obtained. The effect of mesh refinement on the slugging behavior prediction was discussed.