Structure of the sporoderms of fossil spores according to the results of ion etching

The method of ion etching made it possible to observe thin components of the sporoderm (coat) structure of the fossil spores of coal-forming plants under the microscope in reflected light. Channels connecting the sporoderm with the internal parts of spores (cytoplasm), exine material spheroids separated from the coat, and the relief components of the sporoderm surface were detected for the first time. Considerations for the applicability of statistical data on sporoderm thickness and surface relief to the evaluation of the climatic conditions of ancient peat (coal) accumulation and variations in the intensity of ultraviolet radiation from the sun are given.     

EVALUATION OF LEACHING CONDITIONS FOR DISSOLUTION OF PYRITE IN CHLORINE-SATURATED WATER

The optimum leaching conditions for the dissolution of pyrite in water saturated with chlorine gas were investigated. Reaction temperature, solid-to-liquid ratio, reaction time, and particle size were selected as the leaching parameters. 2ⁿ factorial experimental design and orthogonal central-composite design methods were used. A mechanical stirring speed of 500 rpm and chlorine gas-flow rate of 1379 mL/minute were chosen as the fixed parameters in all experiments. The degrees of effectiveness from high to low were found to be, in respective order, the particle size, the reaction temperature, the solid-to-liquid ratio, and leaching time. A reaction temperature of 30°C, solid-to-liquid ratio of 0.167 g/mL, particle size of 150–212 μm, and reaction time of 360 minutes were found to be the optimum leaching conditions. The dissolution yield of iron from pyrite was 98.4% under optimal leaching conditions.     

Phase separation in the synthesis of styrene–divinylbenzene copolymers with di-2-ethylhexyl phthalate as diluent

Phase separation by suspension copolymerization of styrene–divinylbenzene (DVB) with di-2-ethylhexyl phthalate (DOP) as diluent was investigated using equilibrium swelling, swelling rate, apparent densities, and mercury porosimetry. The copolymer prepared in the absence of DOP is heterogeneous, showing that a phase separation exists in the polymerization system, and, in the presence of DOP, the propagating copolymer separates earlier. Furthermore, with increasing amounts of DVB, phase separation occurs earlier than gelation, which causes a sudden increase in the amount of pores about 200–500 Å in diameter corresponding to the interstices between the microspheres.     

Numerical analysis on corrosion resistance of mild steel structures

Corrosion resistances of mild steel specimens according to artificial neural network (ANN) analysis were investigated in the scope of this study. Corrosion rate values were taken into numerical analysis as a result of experimental studies under corrosive aggressive media. Mild steel specimens were selected according to the section type varieties such as box, tube and cornier. All steel specimens were subjected to the aggressive media formed using sodium chloride (NaCl with 99.8 % purity) solutions with 3.5, 5.0 and 7.0 % ratios per one liter distilled water and only distilled water. The reduction in corrosion rate has been observed and considered according to some corrosion loss respects. Corrosion rate prediction models were established between corrosion rate and parameters such as mass loss obtained by experimental studies using ANN. ANNs are computing systems that simulate the biological neural systems of the human brain. In this study, ANN analysis was generated to predict the corrosion rate values after experimental studies. Experimental and predicted values were compared by each other and it is seen that a strong relationship was established between them.     

Insoluble poly(ethylene oxide) nanofibrous coating materials: effects of crosslinking conditions on the matrix stability

In this study, the effect of crosslinking conditions was investigated to obtain insoluble poly(ethylene oxide) (PEO) nanofiber mats having an ultraviolet (UV) initiating and crosslinking agent, pentaerythritol triacrylate (PETA), with various ratios in the presence or absence of UV irradiation at 366 nm. At first, PEO nanofibers were electrospun from 400,000 and 600,000 g/mole molecular weights of PEO and they were compared in terms of diameter and fiber morphology. Whereas applied voltage in the range of 10–25 kV had no significant effect on the fiber morphology, fiber diameters varied by voltage. An increase in the flow rate from 0.25 to 1.00 mL h^?1 had an effect in favor of fabricating thicker fibers. The effect of distance to collector on the diameter and morphology was not distinctive. Fibers having irregular morphology and beads appeared with increasing the polymer concentration from 4 to 8 % w/v. Prior crosslinking, electrospinning process at selected conditions was applied to the PEO (600,000) including PETA and PEO-PETA nanofibers were obtained. Besides PETA concentration and UV application, drying conditions before UV irradiation were also found effective to obtain stable fibers in aqueous media. PEO nanofibers electrospun in the presence of 10 % PETA (w/w), dried for 8 days at 37 °C in an air atmosphere and then, irradiated with UV for 50 min were found most stable in aqueous media. However, crosslinking was also achieved in the absence of UV.

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Investigation of the substrate effect for Zr doped ZnO thin film deposition by thermionic vacuum arc technique

ZnO is a fundamental wide band gap semiconductor. Especially, doped elements change the optical properties of the ZnO thin film, drastically. Doped ZnO semiconductor is a promising materials for the transparent conductive oxide layer. Especially, Zr doped ZnO is a potential material for the high performance TCO. In this paper, ZnO semiconductors were doped with Zr element and microstructural, surface and optical properties of the Zr doped ZnO thin films were investigated. Zr doped ZnO thin films were deposited thermionic vacuum arc (TVA) technique. TVA is a rapid and high vacuum deposition method. A glass, polyethylene terephthalate and Si wafer (111) were used as a substrate material. Zr doped ZnO thin films deposited by TVA technique and their substrate effect investigated. As a results, deposited thin films has a high transparency. The crystal orientation of the films are in polycrystal formation. Especially, substrate crystal orientation strongly change the crystal formation of the films. Substrate crystal structure can change the optical band gap, microstructural properties and deposited layer formation. According to the atomic force microscopy and field emission scanning electron microscopy measurements, all deposited layer shows homogeneous, compact and low roughness. The band values of the deposited thin film were approximately found as to be 3.1–3.4 eV. According to the results, Zr elements created more optical defect and shifted to the band gap value towards to blue region.     

Estimating emissions on vehicular traffic based on projected energy and transport demand on rural roads: Policies for reducing air pollutant emissions and energy consumption

This study deals with the estimation of emissions caused by vehicular traffic based on transport demand and energy consumption. Projected transport demand is calculated with Genetic Algorithm (GA) using population, gross domestic product per capita (GDPPC) and the number of vehicles. The energy consumption is modelled with the GA using the veh-km. The model age of the vehicles and their corresponding share for each year using the reference years is obtained. The pollutant emissions are calculated with estimated transport and energy demand. All the calculations are made in line to meet the European standards. For this purpose, two cases are composed. Case 1: Emissions based on energy consumption, and Case 2: Emissions based on transport demand. The both cases are compared. Three policies are proposed to control demand and the emissions. The policies provided the best results in terms of minimum emissions and the reasonable share of highway and railway mode as 70% and 30% usage for policy I, respectively. The emission calculation procedure presented in this study would provide an alternative way to make policies when there is no adequate data on emission measurement in developing countries.     

Removal of phosphates from aqueous solutions by using bauxite II: the activation study

In this study, acid treatment and heat treatment methods have been investigated in order to enhance the phosphate adsorption capacity of bauxite. For this purpose, a series of bauxites treated with 0.1–1.0 M HCl and another one heated at various temperatures between 200 and 1000 °C were subjected to standardized orthophosphate adsorption tests. Besides determining chemical and mineralogical compositions, TGA and DTA were performed and point of zero net proton charge (PZNPC), surface area, mean particle size and porosity were measured for selected samples. The results have shown that the acid treatment of bauxite has a negative effect on the phosphate adsorption capability. On the other hand, it has been observed that the phosphate adsorption capacity of bauxite could be increased by heating. The optimum heating temperature was determined as 600 °C. Bauxite heated at 600 °C exhibited about an eight‐fold increase in surface area compared with raw bauxite. The results showed that the activation of bauxite occurred via dehydration of boehmite and diaspore, being the hydrated mineral phases. Maximum adsorption efficiencies for ortho‐, tripoly‐ and glycerophosphates were achieved in the slightly acidic pH range. It was found that the adsorption capacities of thermally‐activated bauxite for all phosphate species investigated were higher than that of raw bauxite. But the increase in adsorption efficiency is not proportional to the increase in specific surface area. It was found that the relative adsorptivity of phosphate species investigated is in the order of orthophosphate > tripoly(phosphate) > glycerophosphate. In addition, it was found that the desorption trends of these phosphate species were similar to the results obtained for raw bauxite. Copyright © 2003 Society of Chemical Industry