Pt/十六烷基三甲基溴化铵纳米聚集体修饰玻碳电极促进析氢(英文)

A novel, cost-effective, and simple electrocatalyst based on a Pt-modified glassy carbon electrode(GCE), using cetyltrimethylammonium bromide(CTAB) as a cationic surfactant, is reported. Amphiphilic CTAB molecules were adsorbed on GCE by immersion in a CTAB solution. The positively charged hydrophilic layer, which consisted of small aggregates of average size less than 100 nm,was used for accumulation and complexation of [PtCl2. anions by immersing the electrode in Ksolution. The modified electrode was characterized using scanning electron microscopy,energy-dispersive X-ray spectroscopy, impedance spectroscopy, and electrochemical methods. The electrocatalytic activity of the Pt particles in the hydrogen evolution reaction(HER) was investigated.The results show that the CTAB surfactant enhances the electrocatalytic activity of the Pt particles in the HER in acidic solution.     

Biostratigraphy of Asmari Formation in Ghare Agha seyed of Farsan region,Chaharmahale Bakhtiari Province,Iran

The Asmari Formation consists of shallow marine sedimentary rocks deposited on ramp setting .Lar-ger benthic foraminifera collected from Asmri Formation are dominated by hyaline and porcelanouse forms , in-cluding Amphistegina, Nummulites, Archaias, Astrotrillina, Miogypsinella, Miogypsinoides, Lepidocyclina, Operculina, Spiroclypeous and Miliolids.The presence of Nummulites cf.vascus in the lower part of the forma-tion allows the age to be determined as Rupelian .The occurrence of Borelis pygmae is an index taxon of the Ru-pelian-Chattian and indicates Early Chattian of SBZ 21-22 in the study section .The first appearance of Mio-gypsinella akadagensis shows Late Chattian ( SBZ 23) and defines the upper boundary of the SBZ 21-22.The new data are the first evidences showing that the shallow marine Asmari Formation is attributed to Oligocene (Rupelian-Chattian) age for this region.     

Numerical modeling of flow in riverine basins using an improved dynamic roughness coefficient

Various parameters such as bed and bank materials, shape and irregularity of the section, vegetation, river meanders, plan of the river path etc. affect the flow hydraulic resistance. In open channel hydraulics the effects of all these parameters are generally considered as the roughness coefficient. The Manning’s equation is one of the most practical equations to flow resistance analysis, in which the surface roughness is defined by Manning coefficient. Since many parameters are effective on the value of this coefficient, in this research study it was tried to define the roughness coefficient somehow that it be able to dynamically change with different river and hydraulic conditions. The collected data in Karun River (Iran) for two periods were used as the case study. It is shown that the accuracy of model predictions for water surface elevations were improved more than 13% in error estimation in comparison with the corresponding results obtained for a constant roughness coefficient. The roughness coefficient (n) for Karun River was also estimated using the empirical method proposed by Cowan for two different dry and wet periods. These values were then successfully compared with the average corresponding roughness coefficients calculated by the numerical model for those periods.     

Investigating extreme scenarios with multiple-point geostatistics and variance maximization

Stochastic Environmental Research and Risk Assessment - In many geoscience applications, the data extracted from environmental variables are very limited. Multiple-point geostatistical (MPS)...     

A BEM–FEM approach for analysis of distresses in pavements

A combined boundary-element–finite-element method is presented for the analysis of distresses in pavements subjected to mechanical and environmental effects. Owing to the spatial dimensions of the problem, the non-homogeneity and the irregular geometry at the pavement joints, a combination of the two methods proves to offer a more realistic solution technique. The advantage of the finite element method (FEM) is in its capabilities of modelling near-field regions at or around the vicinity of the joint, whereas the boundary element method (BEM) is more suitable to model the far-field region at infinity. The three major distresses affecting the serviceability of the pavement system are the temperature, moisture and the applied mechanical loads. The model analyses the stresses and strains resulting from both mechanical and environmental factors in the analysis of a pavement system. Moreover, the infiltration of water through pavement joints, which causes weakening of the subgrade soil, is also analysed. Secondly the curling of the pavement concrete slab under the mechanical and thermal loads and induced friction may cause separation of the pavement structure from its supporting subgrade. Both are treated and modelled in this study. A detailed analysis of the pavement joint with its load transfer device is also performed for the proper assessment of the separation and further extension of the loss of support in the pavement system.     

Cyclostratigraphy across a Mississippian carbonate ramp in the Esfahan–Sirjan Basin,Iran: implications for the amplitudes and frequencies of sea-level fluctuations along the southern margin of the Paleotethys

International Journal of Earth Sciences - The Tournaisian–Visean carbonate successions of the Esfahan–Sirjan Basin (ESB) from Sanandaj–Sirjan Zone, Iran, have been used to...     

Investigation of meteorological extreme events over coastal regions of Iran

In this study, in order to detect probable trends and effects of climatic extreme events of precipitation and temperature as well as maximum relative humidity, dew point temperature, sunshine hours, and wind speed, 12 stations on the northern and southern coastlines of Iran were investigated from 1977 to 2007. For this purpose, 27 indices of precipitation and temperature, which are specified by the Expert Team of the World Meteorological Organization and Climate Variability and Predictability, were calculated by using RClimDex software. The Mann?CKendall method was also used to detect possible trends in the data time series. The results indicate that temperature indices are absolutely consistent with warming. Warm nights, hot days, and hot day and night frequencies increased, while cold spell and cool day and night frequencies declined. The minimum temperature experienced a considerable rise both in its maximum and minimum values. The minimum temperature had a higher increase than the maximum temperature. Therefore, diurnal temperature ranges have experienced dramatic declines. In the northern coastal sites, hot day frequency and hottest day temperature showed higher magnitudes than those of the southern sites as a result of the significant increase in the maximum sunshine hours in northern stations. This enhancement led to a considerable increase in the maximum wind speed. Consequently, relative humidity declined in the northern sites. Precipitation indices indicate few significant trends over the studied period. Temporal precipitation distribution was different from station to station. Three precipitation patterns were detected at individual stations, although an overall regional rainfall pattern was not detectable. On the whole, the results of this study emphasize that the water resources in the studied area are going to become problematic.     

Two-phase SPH modelling of waves caused by dam break over a movable bed

This paper describes the application of the Smoothed Particle Hydrodynamics（SPH） method for modeling two dimensional waves caused by dam break over a movable bed in two dimensions.The two phase SPH method is developed to solve the Navier-Stokes equations.Both fluid and sediment phases are described by particles as weakly compressible fluids and the incompressibility is achieved by the equation of state.The sediment phase is modeled as a non-Newtonian fluid using three alternative approaches of artificial viscosity and Bingham Model.In this paper,the new formulations for two-phase flows are proposed.The numerical results obtained from the developed SPH model show acceptable accuracy with comparison to experimental data.     

Mineralogical and geochemical studies on the Gowd-e-Morad (Ni,Co, As–Cu) mineral deposit,Anarak (central Iran)

The Ni, Co, As, and Cu deposit of Gowd-e-Morad is located 20 km northwest of Anarak in Central Iran. In this hydrothermal deposit, mineralization occurs as veins in a fault breccia zone hosted by the Chahgorbeh (schist and metabasite) complex. The main ores are made up of Ni, Co, and Cu arsenides. Petrologic studies and results obtained from geochemical analyses have indicated that the Ni, Co, As, and Cu are derived from ultramafic rocks while Pb and Zn are likely to be derived from schist. Based on the geochemical evidence, particularly the high correlation between Ni, Co, and As, it is proposed that this deposit be categorized as a “five elements” mineral deposit. Fluid inclusion studies have shown homogenization temperatures (T_H) in the range 113?206 ?C and salinity 3?13.5 % wt eq. NaCl. Therefore this “five elements” mineral deposit has been determined as a low temperature, epithermal deposit type. It is proposed that the low fluid temperatures are a result of an environment of formation which was distal to a volcanogenic source systems and the major influence of meteoric waters in the hydrothermal system.     

Pan coefficient (K p) estimation under uncertainty on fetch

The FAO Penman–Monteith (F-PM) method is a frequently applied approach for calculating the daily reference evapotranspiration (ET₀). This method requires long records of meteorological data, which makes it quite hard to employ in locations with no or limited available data. Evaporation pans are widely used to estimate the reference ET₀, but this method requires reliable estimates of the pan coefficient (K _p). The objectives of this study were to determine the proper values of monthly and annual K _p, as well as the best method among those available for the estimation of K _p values in the study area. Measured weather data from 1992 to 2006 were obtained from 18 stations in the North and Northwest of Iran. Daily ET₀ calculated using methods by Bernardo et al. and Pereira et al. were compared with those calculated by the F-PM method. The employed methods at all stations, except those located in the north of the study area with high relative humidity, overestimated the ET₀ compared to the F-PM method. The constant parameters of these methods were optimized by a trial and error scheme to minimize the root mean square error. The results indicated that modified K _p coefficients from Bernardo et al.’s method ranged between 0.41 and 0.87 and the optimal coefficient of Pereira et al.’s method ranged between 0.49 and 0.95. Modified monthly K _p from Bernardo et al.’s method ranged between 0.3 and 1.07 and those from Pereira et al.’s method ranged between 0.4 and 1.18. Modified K _p of the methods by Bernardo et al. and Pereira et al. showed the higher estimation accuracy of daily ET₀ values. In general, the performance of the modified K _p of Bernardo et al.’s method was higher than Pereira et al.’s method for all stations. Thus, in the study region and under the same climatic conditions [in areas with only pan evaporation (E _p) records], the use of climatic monthly modified K _p to calculate ET₀ based on class A E _p is recommended.