This paper presents a class of routing protocols called road-based using vehicular traffic (RBVT) routing, which outperforms existing routing protocols in city-based vehicular ad hoc networks ...(VANETs). RBVT protocols leverage real-time vehicular traffic information to create road-based paths consisting of successions of road intersections that have, with high probability, network connectivity among them. Geographical forwarding is used to transfer packets between intersections on the path, reducing the path's sensitivity to individual node movements. For dense networks with high contention, we optimize the forwarding using a distributed receiver-based election of next hops based on a multicriterion prioritization function that takes nonuniform radio propagation into account. We designed and implemented a reactive protocol RBVT-R and a proactive protocol RBVT-P and compared them with protocols representative of mobile ad hoc networks and VANETs. Simulation results in urban settings show that RBVT-R performs best in terms of average delivery rate, with up to a 40% increase compared with some existing protocols. In terms of average delay, RBVT-P performs best, with as much as an 85% decrease compared with the other protocols.
Tropical and sub-tropical South America are highly susceptible to extreme droughts. Recent events include two droughts (2005 and 2010) exceeding the 100-year return value in the Amazon and recurrent ...extreme droughts in the Nordeste region, with profound eco-hydrological and socioeconomic impacts. In 2015-2016, both regions were hit by another drought. Here, we show that the severity of the 2015-2016 drought ("2016 drought" hereafter) is unprecedented based on multiple precipitation products (since 1900), satellite-derived data on terrestrial water storage (since 2002) and two vegetation indices (since 2004). The ecohydrological consequences from the 2016 drought are more severe and extensive than the 2005 and 2010 droughts. Empirical relationships between rainfall and sea surface temperatures (SSTs) over the tropical Pacific and Atlantic are used to assess the role of tropical oceanic variability in the observed precipitation anomalies. Our results indicate that warmer-than-usual SSTs in the Tropical Pacific (including El Niño events) and Atlantic were the main drivers of extreme droughts in South America, but are unable to explain the severity of the 2016 observed rainfall deficits for a substantial portion of the Amazonia and Nordeste regions. This strongly suggests potential contribution of non-oceanic factors (e.g., land cover change and CO2-induced warming) to the 2016 drought.
► CuO nanosheet arrays on nickel foam are prepared via a facile one-step method. ► Nanosheet array CuO exhibits a high specific capacitance of 569
F
g
−1 in KOH solution. ► CuO nanosheet arrays ...electrode has porous structure and high utilization of CuO.
CuO nanosheet arrays freely standing on nickel foam are prepared via a template-free growth method. The morphology of CuO nanosheet arrays is examined by scanning and transmission electron microscopy and the phase structure of nanosheets is analyzed by X-ray diffraction spectroscopy. The supercapacitance of CuO nanosheet arrays is investigated by cyclic voltammetry, galvanostatic charge/discharge test and electrochemical impedance spectroscopy. The results show that the array of CuO nanosheets forms a uniform film of around 5
μm in thickness on nickel foam skeleton. The film is composed of clusters of arrays of nanosheets with a thickness up to around 150
nm. The CuO nanosheet arrays exhibit a specific capacitance of 569
F
g
−1 at a current density of 5
mA
cm
−2 in 6.0
mol
dm
−3 KOH electrolyte. The capacitance loss is less than 17.5% after 500 charge/discharge cycles at 10
mA
cm
−2 and with columbic efficiency higher than 93%.
•Ni-Co NWAs electrode was fabricated by polycarbonate template.•Ni-Co NWAs electrode with 10% of Co molar ratio shows best catalytic activity.•Direct urea/H2O2 fuel cell shows high output performance ...with Ni-Co NWAs anode.
Nickel-cobalt nanowire arrays (Ni-Co NWAs) electrode is prepared by one-step galvanostatic electrodeposition with a polycarbonate membrane as the template. By adjusting the Co proportion in the Ni and Co bath solution into 10%, the optimal Ni-Co NWAs electrode in terms of relatively lower onset potential and highest current density towards urea electro-oxidation is obtained. Its catalytic performance is investigated by constructing single direct urea/hydrogen peroxide (H2O2) fuel cell. Results show that a peak power density of 7.4mWcm−2 and an open circuit voltage of 0.92V are achieved at room temperature when 9.0molL−1 KOH and 0.33molL−1 urea are used as the anolyte, H2SO4 and H2O2 as the catholyte. Additionally, the urea/H2O2 fuel cell also demonstrates excellent stability during short term duration test.
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•Both indirect oxidation and direct urea electro-oxidation paths exist on nickel.•Rate determining step depends on polarization potential and KOH concentration.•Nickel catalyst is ...poisoned by the CO2 intermediate.
Urea electro-oxidation reaction in alkaline medium is systematically analyzed by electrochemical impedance spectroscopy (EIS). The effects of polarization potential and KOH concentration on the impedance appearance are investigated. In the presence of urea, it is found that Nyquist plots exhibit two depressed semicircles, with one at higher frequencies stably locating in the first quadrant while the other’s location at lower frequencies varying between the first and second quadrant as the polarization potential changes. Results show both indirect and direct pathways proceed in urea electro-oxidation reaction. A mathematical model indicates the reverse loop in the Nyquist plots is attributed to CO2 poisoning on the catalyst, which is also validated by the followed chronoamperometric method. Moreover, the rate determining steps of urea electro-oxidation reaction is dependent on KOH concentration. The EIS technique gives a new sight to interpret the poor stability of urea electro-oxidation on nickel catalyst, and thus helps to explore a CO2-insensitive catalyst.
Geothermal energy is considerably encouraged by governments because it offers a low-carbon renewable option to satisfy the long-term heat demand. However, to date research on systematic and ...scientific evaluations of the environmental benefits of geothermal heating is limited. Therefore, compared with the traditional coal-fired heating system, the cleanliness of geothermal heating is examined by employing the life cycle assessment approach in this study. Results show that the environmental impacts of geothermal heating are considerably less than those of coal-fired heating, and geothermal heating with water reinjection is the most ideal scenario. Environmental benefits linearly increase with the injection rate growth of geothermal water. Compared with coal-fired heating for per GJ of heat generation, geothermal heating can lead to 77%, 76%, and 78% reductions in terms of particulate formation, carbon emission, and fossil energy depletion, respectively. The electricity consumption process is the main contributor to the overall environmental burden of geothermal heating. Instead of coal power for geothermal heating, the actual hybrid electricity of China in 2017 (i.e., 64.7% coal power, 18.6% hydropower, 4.7% wind power, 1.8% solar energy) can lead to 27%, 33%, and 27% reductions in fossil depletion, carbon emission, and particulate formation for per GJ of heat production, respectively. These findings not only indicate the feasibility of using geothermal resources to address carbon emissions, energy crisis, and air quality issues, but also demonstrate benefits for human health and ecosystem quality. Furthermore, the results highlight the importance of generating electricity with clean energy in geothermal heating. Thus, generating electricity with clean energy instead of coal is necessary to further reduce the environmental impact of geothermal heating.
•Geothermal heating with geothermal water reinjection is the most ideal scenario.•Electricity generation is the key process in geothermal heating.•Environmental benefits linearly increase with the injection rate of geothermal water.•Geothermal heating can reduce carbon emissions by 76% compared to coal heating.•33% of carbon emission can be saved with mixed energy in geothermal heating scenario.
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