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.
A facile one-step pyrolysis and activation synthesis method is utilized to convert a common biomass of willow catkin into interconnected porous carbon nanosheets (PCNs), and then followed by ...effective nitrogen and sulfur co-doping. Owing to the unique hollow and multilayered structure of willow catkin fiber, the pore structure of obtained carbons can be controlled by adjusting the mass ratio of raw material to alkali. As a result, the nitrogen and sulfur co-doped PCNs demonstrate a high specific capacitance of 298Fg−1 at 0.5Ag−1 and 233Fg−1 at 50Ag−1, revealing excellent rate performance. In addition, the electrode demonstrates superb cycling stability with only 2% capacitance loss after 10,000 cycles. Furthermore, the assembled symmetric cell with a wide voltage range of 1.8V yields a remarkable specific energy of 21.0Whkg−1 at 180Wkg−1. These exciting results exhibit a green and low-cost design of electrode materials for high performance supercapacitors.
The willow catkin derived nitrogen and sulfur co-doped porous carbon nanosheets (N,S-PCNs1-1) are prepared by a facile one-step pyrolysis and activation synthesis method, and then followed by effective nitrogen and sulfur co-doping. As a result, the as-obtained carbon processes cross-linked graphene-like structure with high specific surface area and interconnected pore texture, resulting in high specific capacitance, excellent rate performance and cycling stability.
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•Willow catkin is effectively converted into cross-linked porous carbon nanosheets.•N,S-PCNs1-1 electrode shows excellent capacitive performance.•The assembled symmetric supercapacitor exhibits high energy density.
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.
Hot dry rock (HDR) is an important geothermal resource and the primary direction of future geothermal development. Granite is particularly rich in radiogenic heat-generating elements (e.g., U, Th, ...and K) and is thus the main target for HDR development worldwide. Southeastern China contains the most abundant granite distribution in the country and accounts for more than 40% of the total granite area. This paper analyzes the rock radiogenic heat production, geothermal flux, crustal thermal structure, and reservoir temperature in the key exploration areas based on a systematic investigation of the distribution of granite resources and their heat generation characteristics. A heat generation and accumulation model of HDR resources is proposed for southeastern China. The results show that southeastern China can be characterized by a quadratic heat gathering model that includes a mantle source heat supply, intracrustal heat generation, fracture heat transfer, and cover heat preservation. Among these, the radiogenic heat production of granite is one of the main factors that affects shallow geothermal fields in this region. Fracture structure and cover conditions also exert a strong control on the gathering and dissipation of underground heat. The widely distributed and high-heat-producing tuffs and fused tuffs in the Zhangzhou area offer promising heat-generating and heat-gathering conditions for future exploration and development of hot dry rock resources in the area. The results provide important insight on the genesis and heat control factors of HDR resources in southeastern China and a theoretical reference for future HDR resource exploration and development practices in the region.
► 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.
Medium-low temperature geothermal resources in the Wumishan Formation, which is the geothermal reservoir, are local enrichment resources in Xiong'an New Area, North China. In this study, 35 water ...samples were collected from the bedrock of Taihang Mountains and Wumishan Formation in Xiong'an New Area and display the chemical compositions of water samples as well as the stable isotope compositions for hydrogen, oxygen, carbon, sulfur, and strontium. Hydrogeochemical characteristics and isotope compositions of water samples are analyzed to understand the origin and circulation processes of these geothermal fluids. Our results of cold groundwaters in the bedrock of Taihang Mountain indicate a more open oxidation environment, and the HCO3-CaMg-type groundwater also indicates a prevailing carbonate dissolution condition. The deep geothermal fluids in the Wumishan Formation beneath Xiong'an New Area indicate a closed reduction condition, and their hydrochemical types are mainly Cl HCO3-Na type. The diagram of hydrogen vs. oxygen isotope indicates that the recharge for the deep geothermal fluids in the Wumishan Formation of Xiong'an New Area is mainly from atmospheric precipitation. The high δ13C values (-3.4 ppm to -4.9 ppm) are notably controlled by the eluviation of the carbonate rock layers. The δ34S values vary from 18.02 ppm to 27.01 ppm; the relatively high values indicate the eluviation of sedimentary rock layers. The high 87Sr/86Sr ratios (0.70806-0.71270) and the high Sr2+ concentrations (0.69-2.92 mg/L) suggest that the Sr in the deep geothermal fluids originates from the eluviation of both silicates and carbonates. According to the multimineral equilibrium diagram, chalcedony is saturated at the measured temperature of geothermal wells; therefore, we chose chalcedony as a geothermal thermometer for the calculation of the reservoir temperature of the Wumishan Formation, and the results vary from 68.63 to 89.10°C. Our study identifies the geothermal type of the deep medium-low temperature hydrothermal systems and also recognizes their water-rock interaction processes. We get a comprehensive understanding that the geothermal resources in the Wumishan Formation beneath Xiong'an New Area is convection-conduction type, for which potential of geothermal development and utilization is enormous.
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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.
Advances in the exploration of the geothermal resources with remarkably high temperatures in the Gonghe Basin, northeastern Tibetan Plateau, provide an enhanced understanding of the origin and ...emplacement of hot dry rock (HDR). Based on the integrating analysis on the boundary faults distribution and their activity histories, springs and geothermal borehole data, and magnetotelluric data, we propose that the Gonghe Basin formed in a zone of slip dissipation between two major large-scale left-lateral strike-slip faults of the Kunlun fault to the south and the Haiyuan fault to the north during the Neogene time. During the evolution of these two major strike-slip faults, the basin has experienced two-phase developments: the transrotational Gonghe-Qinghai lacustrine basin system during the Miocene and the transpressional Gonghe-Tongde basin system during the Pliocene-Quaternary. In response to the crustal transtension components of the transrotational Gonghe Basin, the partial melting zone at depths of 10-25 km in the thickened crust (∼54 km) has been uplifted by ∼10 km compared with adjacent regions since the Pliocene. This uplifted partial melting zone may have provided prominent potential heat energy for the HDR in the Triassic granitoid batholith at shallower depths (∼3-10 km) by effective enhancement of the geothermal conduction process via deep faulting. With obliquely south-verging thrusting of the Gonghe Nan Shan thrusts in the northern, the Gonghe Basin has transformed from transrotation to transpression-domination during the 6-3 Ma, as well as accompanying with the depocentre migrating to the northwest and in turn the basement elastically uplifting in the southeast. This differential deformation of the basin floor has resulted in a northeastward upward tilting of the Triassic batholith and an isothermal surface. It finally developed the high-temperature and shallow-burial HDR with anomalously temperatures of over 100°C at a depth of 1.5 km in the Qiabuqia and Zhacang geothermal areas in the Gonghe Basin, NE margin of the Tibetan Plateau.
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