Surface Coverage Algorithm in Directional Sensor Networks for Three-Dimensional Complex Terrains

Coverage is an important issue in the area of wireless sensor networks, which reflects the monitoring quality of the sensor networks in scenes. Most sensor coverage research focuses on the ideal two-dimensional （2-D） plane and full three-dimensional （3-D） space. However, in many real-world applications, the target field is a 3-D complex surface, which makes conventional methods unsuitable. In this paper, we study the coverage problem in directional sensor networks for complex 3-D terrains, and design a new surface coverage algorithm. Based on a 3-D directional sensing model of nodes, this algorithm employs grid division, simulated annealing, and local optimum ideas to improve the area coverage ratio by optimizing the position coordinates and the deviation angles of the nodes, which results in coverage enhancement for complex 3-D terrains. We also conduct extensive simulations to evaluate the performance of our algorithms.

Comparison of spatial structures of urban agglomerations between the Beijing-Tianjin-Hebei and Boswash based on the subpixel-level impervious surface coverage product

Under the background of China's rapid urbanization, study on comparative analysis of the spatial structure of urban agglomerations between China and the US can provide the policy proposals of space optimization for the Chinese government. Taking the Beijing-Tianjin-Hebei(BTH) and Boswash as study area, we mapped the subpixel-level impervious surface coverage of the BTH and Boswash, respectively, from 1972 to 2011. Further, landscape metrics, gravitational model and spatial analysis were used to analyze the differences of the spatial structures between the BTH and Boswash. The results showed that(1) the area of the impervious surface increased rapidly in the BTH, while those remained stable in the Boswash.(2) The spatial structure of the BTH experienced different periods including isolated cities stage, dual-core cities stage, group cities stage and network-style cities stage, while those of the Boswash was more stable, and its spatial pattern showed a "point-axis" structure.(3) The spatial pattern of high-high assembling regions of the impervious surface exhibited a "standing pancake" feature in the BTH, while those showed a "multi-center, local aggregation and global discrete" feature in the Boswash.(4) All the percentages of the impervious surface of ecological, living, and production land of the BTH were higher than those of the Boswash. At last, from the perspective of space optimization of urban agglomeration, the development proposals for the BTH were proposed.

Erosion and covered zones altered by surface coverage effects on soil nitrogen and carbon loss from an agricultural slope under laboratorysimulated rainfall events

Soil erosion,one of the most serious environmental concerns,might remove topsoil and essential element from terrestrial land.However,few attentions have been given to investigating how soil erosion regimes affect soil carbon and nitrogen loss.Therefore,this study investigated the effects of surface coverage rates(83%,67%,50%,33%,17%and 0%)and two positions(up-and downslope)on erosion regimes and its associated soil nitrogen and carbon loss under a sequence of six rainfalls(R1-R6).These results showed that the sediment concentrations with 33%(R4)and 17%(R5)coverage downslope were significantly lower than those with coverage upslope,whereas there was no significant difference between the runoff rates of the two slopes.Thus,surface coverage at different positions induced two soil erosion regimes(deposition-and transport-dominated processes).Dynamics of the DON and DIN concentrations indicated different release processes of soil nitrogen into runoff.The DON contributed to a substantial amount of soil nitrogen loss,which accounted approximately 81%of the organic form.The SBOC is significantly correlated with sediment-enriched clay particles from the deposition-dominated processes and is higher than that from the transport-dominated processes.The DOC is significantly correlated with Rr for transport-dominated processes.These results illustrated the critical role of erosion regimes in soil organic carbon loss in dissolved or sediment-bound form.It is concluded that erosion/covered zones altered by surface coverage could produce transport-and deposition-dominated erosion regimes and consequently affect soil carbon and nitrogen loss.In addition,these results demonstrated that surface coverage pattern may efficiently control soil erosion and soil carbon and nitrogen loss.

Preliminary Model Study for Forecasting a Hot Weather Process in Guangdong Province Using CMA-TRAMS

In this paper, the CMA-TRAMS tropical high-resolution system was used to forecast a typical hot weather process in Guangdong, China with different horizontal resolutions and surface coverage. The results of resolutions of 0.02° and 0.06° were presented with the same surface coverage of the GlobeLand30 V2020, companies with the results of resolution 0.02° with the USGS global surface coverage. The results showed that, on the overall assessment the 2 km model performed better in forecasting 2 m temperature, while the 6 km model was more accurate in predicting 10 m wind speed. In the evaluation of representative stations, the 2 km model performed better in forecasting 2 m temperature and 2 m relative humidity at the coastal stations, and the 2 km model was also better in forecasting 2 m pressure at the representative stations. However, the 6 km model performed better in forecasting 10 m wind speed at the representative stations. Furthermore, the 2 km model, owing to its higher horizontal resolution, presented a more detailed stratification of various meteorological field maps, allowing for a more pronounced simulation of local meteorological element variations. And the use of the surface coverage data of the GlobeLand30 V2020 improved the forecasting of 2 m temperature, and 10 m wind speed compared to the USGS surface coverage data.

Kinetic simulation of oxidative coupling of methane over perovskite catalyst by genetic algorithm:Mechanistic aspects

The reaction kinetics of oxidative coupling of methane catalyzed by perovskite was studied in a fixed bed flow reactor.At atmospheric pressure,the reactions were carried out at 725,750 and 775℃,inlet methane to oxygen ratios of 2 to 4.5 and gas hourly space velocity （GHSV） of 100 min^-1.Correlation of the kinetic data has been performed with the proposed mechanisms.The selected equations have been regressed with experimental data accompanied by genetic algorithm （GA） in order to obtain optimized parameters.After investigation the Langmuir-Hinshelwood mechanism was selected as the best mechanism,and Arrhenius and adsorption parameters of this model were obtained by linear regression.In this research the Marquardt algorithm was also used and its results were compared with those of genetic algorithm.It should be noted that the Marquardt algorithm is sensitive to the selection of initial values and there is possibility to trap in a local minimum.

Effect of Outer Carbon Layer Thickness of Carbon-covered N-doped Hollow Carbon Nanospheres on Its Electrocatalytic Performance

Hollow nitrogen-doped porous carbon materials covered with different thicknesses of carbon layers were synthesized to assist evaluation of the influence of nitrogen atom on the surrounding carbon atoms.The designed carbon-based materials were synthesized through pyrolysis of surface-attached block copolymer layers on silica nanoparticles with different thicknesses of the second block of grafted polymer chains,followed by removal of silica templates.The experimental results reveal that coverage a carbon layer with proper thickness can improve the oxygen reaction reduction activity of nitrogen-doped carbon materials as evidenced by the positive shift of half-wave potential in linear scanning voltammetry response curves.The conclusions may provide a reference work on understanding the active sites and designing materials with superior electrochemical performance.

Effects of rye grass coverage on soil loss from loess slopes

Vegetative coverage is commonly used to reduce urban slope soil erosion.Laboratory experimental study on soil erosion under grass covered slopes is conventionally time and space consuming.In this study,a new method is suggested to study the influences of vegetation coverage on soil erosion from a sloped loess surface under three slope gradients of 51,151,and 251;four rye grass coverages of 0%,25%,50%,and 75%;and three rainfall intensities of 60,90,and 120 mm/h with a silt-loamy loess soil.Rye grasses were planted in the field with the studied soil before being transplanted into a laboratory flume.Grass was allowed to resume growth for a period before the rain simulation experiment.Results showed that the grass cover reduced soil erosion by 63.90%to 92.75%and sediment transport rate by 80.59%to 96.17%under different slope gradients and rainfall intensities.The sediment concentration/sediment transport rate from bare slope was significantly higher than from a grass-covered slope.The sediment concentration/transport rate from grass-covered slopes decreased linearly with grass coverage and increased with rainfall intensity.The sediment concentration/transport rate from the bare slope increased as a power function of slope and reached the maximum value at the gradient of about 251,whereas that from grass-covered slope increased linearly and at much lower levels.The results of this study can be used to estimate the effect of vegetation on soil erosion from loess slopes.

Fabrication of compact and stable perovskite films with optimized precursor composition in the fast-growing procedure

The fast-growing procedure （FGP） provides a simple, high-yield and lead （Pb）-release free method to prepare perovskite films. In the FGP, the ultra-dilute per- ovskite precursor solution is drop-cast onto a hot （-240℃） substrate where a perovskite film grows immediately ac- companied by the rapid evaporation of the host solvent. In this process, all the raw materials in the precursor solution are deposited into the final perovskite film. The potential pollution caused by Pb can be significantly reduced. Proper- ties of the FGP-processed perovskite films can be modulated by the precursor composition. While CH3NH3CI （MACI） affects the crystallization process and leads to full surface coverage, CH（NHz）2I （FAI） enhances the thermal stability of the film. Based on the optimized precursor composition of PbI2.（1-x）FAI.xMACI, x=0.75, FGP-processed planar het- erojunction perovskite solar cells exhibit power conversion efficiencies （PCEs） exceeding 15% with suppressed hysteresis and excellent reproducibility.

Effect of fine solid particles on absorption rate of gaseous CO_(2)

The influence of the properties of solid particles in slurry on the absorption of CO_(2) in the slurry was inves-tigated in a stirred thermostatic reactor.The absorption experiments were carried out in three different slurries con-sisting of water,cyclohexane and soybean oil,respectively,and three kinds of solid particles(active carbon,active alu-mina and silica gel)were incorporated into each of the above mentioned slurries separately.The experimental results show that the active carbon particles could enhance the absorption rate of gaseous CO_(2) in the aqueous slurry,while in the cyclohexane slurry,active carbon particles indi-cated no the absorption enhancement effect.However,it was observed that the active alumina and silica gel particles could enhance the absorption rate of CO_(2) in the cyclohex-ane slurry.These phenomena indicate that the solid part-icles,which could enhance the gaseous CO_(2) absorption rate,should possess two properties simultaneously,i.e.they rejected the solvent and had higher adsorption capacity for the solute.The experimental results also show that,as for those solid particles which could enhance the gas absorption rate,the enhancement increased quickly with the increase of solid concentration in slurry at first,and then reached a constant value gradually.It was also found that the enhancement factor was related to the coverage fraction of solid particles on the gas-liquid interface,and due to the reduction of surface fraction with increasing stirred speed,the enhancement factor decreased.

Interfacial engineering of metallic rhodium by thiol modification approach for ambient electrosynthesis of ammonia

Here we report a vapor-phase reaction approach to fabricate rhodium(I)-dodecanethiol complex coated on carbon fiber cloth(Rh(I)-SC_(12)H_(25)/CFC),followed by low-temperature pyrolysis to achieve dodecanethiol modified Rh(Rh@SC_(12)H_(2)5/CFC)for electrocatalytic nitrogen reduction reaction(NRR).The results demonstrate that after pyrolysis for 0.5 h at 150℃,the obtained Rh@SC_(12)H_(2)5/CFC-0.5 exhibits excellent NRR activity with an NH3 yield rate of 121.2±6.6μg∙h^(−1)∙cm^(−2)(or 137.7±7.5μg∙h^(−1)∙mgRh^(−1))and a faradaic efficiency(FE)of 51.6%±3.8%at−0.2 V(vs.RHE)in 0.1 M Na_(2)SO_(4).The theoretical calculations unveil that the adsorption of dodecanethiol on the hollow sites of Rh(111)plane is thermodynamically favorable,effectively regulating the electronic structure and surface wettability of metallic Rh.Importantly,the dodecanethiol modification on Rh(111)obviously decreases the surface H*coverage,thus inhibiting the competitive hydrogen evolution reaction and concurrently reducing the electrocatalytic NRR energy barrier.