First-principles DFT study of SO2 and SO3 adsorption on 2PANI: a model for polyaniline response

Interaction of SO_x (x?=?2,3) molecules on active sites of dianiline (as a model for polyaniline, denoted here as 2PANI) was studied using density functional theory at the BLYP-D/6-31+G(d) level of theory. Natural population analysis was used to find out the charge distribution as well as the net transferred charge of SO_x upon adsorption on 2PANI and the result has been compared with Mulliken charge analysis to evaluate the sensing ability of 2PANI. The computed density of states point to the remarkable orbital hybridization between SO_x and 2PANI during the adsorption process. As a consequence, the results of UV–VIS confirm the sensing ability of 2PANI toward SO₂ and SO₃. Based on our results, it can be found that at proper configuration the SO₂ and SO₃ molecules can be adsorbed on 2PANI with adsorption energies (E_ads) of ?18.2 and ?62.9?kJ/mol (BSSE), respectively.     

Use of average data of 181 synoptic stations for estimation of reference crop evapotranspiration by temperature-based methods

Evapotranspiration has a highlighted role in agricultural and forest meteorology researches, hydrological cycle, irrigation scheduling, and water resources management. There are many models to estimate the evapotranspiration including mass transfer, radiation, temperature, and pan evaporation-based models. This study aims to compare temperature-based models to detect the best model under different weather conditions. For this purpose, weather data were gathered from 181 synoptic stations in 31 provinces of Iran. The evapotranspiration was estimated using 11 temperature-based models and was compared with the FAO Penman-Monteith model. The results showed that the Modified Hargreaves-Samani models estimate the evapotranspiration better than other models in the most provinces of Iran (25 provinces). However, the values of R² were less than 0.98 for 15 provinces of Iran. Therefore, the models were calibrated and preciseness of estimation was increased. However, the estimation was improved only in 14 provinces. The new temperature-based models estimated the evapotranspiration in the eastern (RK, NK, SB, and KE) provinces of Iran (with a various temperature range 14–20 °C) better than other provinces. The best precise methods were the Modified Hargreaves-Samani 1 method for AL (before calibration) and the Modified Hargreaves-Samani 3 method for KE (after calibration). Finally, a list of the best performance of each model has been presented to use other regions and next researches according to values of mean, maximum, and minimum temperature, elevation, minimum and mean relative humidity, sunshine, precipitation, and wind speed. The results are also useful for selecting the best model when we must apply temperature-based models because of type of available data.     

Apparatus for high temperature friction measurement

The static and dynamic coefficient of friction between two flat surfaces at elevated temperature is under investigation. The equipment used in this study was originally designed for the precision glass molding (PGM) process and was then modified for friction measurement. The ultimate aim of this research is to study and characterize the frictional behavior between glass and a mold surface at elevated temperatures typical of the PGM process and under conditions similar to those for this process. This paper describes the design of the apparatus, and validation experiments using a steel-steel material pair at room temperature for comparison with values reported in the literature. The average friction coefficient between the steel-steel pair was found to be 0.17. Subsequent experiments using steel against steel and BK-7 glass against steel, found the stick-slip phenomena is happening at 577 °C.     

Effect of the Size Distribution of Nanoscale Dispersed Particles on the Zener Drag Pressure

In this article, a new relationship for the calculation of the Zener drag pressure is described in which the effect of the size distribution of nanoscale dispersed particles is taken into account, in addition to particle radius and volume fraction, which have been incorporated in the existing relationships. Microstructural observations indicated a clear correlation between the size distribution of dispersed particles and recrystallized grain sizes in the AA7020 aluminum alloy. However, the existing relationship to calculate the Zener drag pressure yielded a negligible difference of 0.016 pct between the two structures homogenized at different conditions resulting in totally different size distributions of nanoscale dispersed particles and, consequently, recrystallized grain sizes. The difference in the Zener drag pressure calculated by the application of the new relationship was 5.1 pct, being in line with the experimental observations of the recrystallized grain sizes. Mathematical investigations showed that the ratio of the Zener drag pressure from the new equation to that from the existing equation is maximized when the number densities of all the particles with different sizes are equal. This finding indicates that in the two structures with identical parameters except the size distribution of nanoscale dispersed particles, the one that possesses a broader size distribution of particles, i.e., the number densities of particles with different sizes being equal, gives rise to a larger Zener drag pressure than that having a narrow size distribution of nanoscale dispersed particles, i.e., most of the particles being in the same size range.     

Numerical investigation of fluid flow and heat transfer around a solid circular cylinder utilizing nanofluid

In this study, flow-field and heat transfer through a copper–water nanofluid around circular cylinder has been numerically investigated. Governing equations containing continuity, N–S equation and energy equation have been developed in polar coordinate system. The equations have been numerically solved using a finite volume method over a staggered grid system. SIMPLE algorithm has been applied for solving the pressure linked equations. Reynolds and Peclet numbers (based on the cylinder diameter and the velocity of free stream) are within the range of 1 to 40. Furthermore, volume fraction of nanoparticles (φ) varies within the range of 0 to 0.05. Effective thermal conductivity and effective viscosity of nanofluid have been estimated by Hamilton–Crosser and Brinkman models, respectively. The effect of volume fraction of nanoparticles on the fluid flow and heat transfer characteristics are investigated. It is found that the vorticity, pressure coefficient, recirculation length are increased by the addition of nanoparticles into clear fluid. Moreover, the local and mean Nusselt numbers are enhanced due to adding nanoparticles into base fluid.     

A Comprehensive Experimental Study on Finishing Aluminum Tube by Proposed UAMAF Process

In this paper, a new noncontact ultrasonic magnetic abrasive finishing mechanism is presented. An ultrasonic vibration producer is used to vibrate the permanent magnets. The ferromagnetic steel grits in the created magnetic field form a flexible finishing tool. To take advantage of cavitation collapse pressure, the finishing zone components are immersed in water. The present work also studies the effect of parameters, i.e., time duration for finishing and working gap between magnetic poles and the workpiece on the surface roughness (Ra). The microscopic pictures and the roughness profile diagrams demonstrate the advantages of the proposed method.     

Very high-speed and high-accuracy current-steering CMOS D/A converter using a novel 3-D decoder

In this paper a 10-bit 1.2-GSample/s Nyquist current-steering CMOS digital-to-analog converter (DAC) is presented. Segmentation (90%) has been used to get the best DNL and reduce glitch energy. This segmentation ratio guarantees the monotonicity. Higher performance is achieved using a novel 3-D thermometer decoding method which reduces the area, power consumption, and the number of control signals of the digital section. Simulation results show that the spurious-free-dynamic-range (SFDR) in Nyquist rate is better than 65 dB for sampling frequency up to 1.2-GSample/s. The analog voltage supply is 3.3 V while the digital part of the chip operates at only 2.4 V. Total power consumption in Nyquist rate measurement is 149 mW. The chip has been processed in a standard 0.35 μm CMOS technology. Active area of chip is 1.97 mm².     

Evaluation of the effect of Ultra Rice® EDTA supplementation on the soluble iron,visual acceptance and vitamin A stability of commercial milled rice blends

The addition of NaFeEDTA at only 5% of total iron to ferric pyrophosphate‐fortified Ultra Rice^® increased the in vitro soluble iron ten‐fold. Ultra Rice^® formulated with NaFeEDTA at 2–7% of total iron, or with Na₂EDTA·2H₂O at 0.5× the total iron equivalents, increased the soluble iron seven‐ to thirty‐fold. The colour of the batches was acceptable through 20 weeks at 21 °C, but colour stability needs to be evaluated under authentic storage conditions. Although only 34–46% of the initial vitamin A remained after extrusion, 18‐week storage at 30 °C/70% relative humidity, and simulated cooking, there were indications that losses could be decreased by raising the pH (to ~5) and/or using a better protected vitamin A ingredient. The enhancement of soluble iron afforded by low‐level NaFeEDTA or Na₂EDTA·2H₂O supplementation suggests that this fortification strategy may merit further study as a means of increasing absorbable iron in Ultra Rice^®.     

Numerical and clinical investigation on the material model of the cornea in Corvis tonometry tests: differentiation between hyperelasticity and viscoelasticity

Mechanics of Time-Dependent Materials - Non-contact tonometers, including ORA and Corvis ST, are not only used to estimate intraocular pressure (IOP) in clinical surveys but are also utilized to...