Background: Incorporation of chemical additives has long been a technique used to improve properties of the gypsum products. The purpose of this work was to study the effects of adding a combination of gum Arabic and calcium hydroxide to a type III dental stone and type IV improved die stone with different proportion. The effect on water/powder ratio, and surface hardness was determined. Material and method: Both material stone and die stone were blended with two proportion of additives so that each material was mixed twice but with different proportion of gum Arabic (0.1% and 0.2%) and calcium hydroxide (0.5 % and 0.3%). Data for hardness were subjected to two-way analysis of variance. Results: The results revealed that the chemical additives were reduced the water requirements of gypsum products so that the reduction of water lead to increase the density of mixture that sets harder. For type III dental stone the additives significantly improved the surface hardness, while for type IV improved die stone the surface hardness was not enhanced except it was designed to be mixed at low water/powder ratio, and in some instances a reduction in hardness was observed, especially at the most reduced water / powder ratio (0.18).
Corrosion of Zn-Ni alloy coatings on stainless steel 316 SS in a chloride-sulfate bath with the addition of either triethanolamine or sucrose was examined. A constant cathode potential was used to deposit zinc-nickel alloys, while cyclic voltammetry and potentio-dynamic polarization were used to measure corrosion. In addition, scanning electron microscopy was utilized to analyse Zn-Ni alloy coating surface layers formed with¬out and with additives. The outcomes discovered that the corrosion resistance of Zn-Ni alloy coat¬ings in 3.5 % NaCl solution was highly influenced by adding triethanolamine or sucrose. Decreasing the Zn:Ni molar ratio led to an increase in corrosion resistance. All Zn-Ni alloy coatings were superior to pure Z
... Show MoreUnter Exilliteratur versteht man „die literarische Produktion von Autoren, die wegen politischer, religiöser oder rassistischer Verfolgung gezwungen sind, sich an einem anderen als dem von ihnen gewünschten Lebens- und Arbeitsort aufzuhalten.“[1] Deswegen unterscheidet sich „Migration“ von „Exil“ dadurch, dass sie freiwillige Auswanderung ist. Bereits in der Antike und auch im Mittelalter gab es Schriftsteller, die vor Zensur oder politischer Verfolgung ins Exil geflohen sind, wie zum Beispiel der griechische Satiriker des
... Show MoreThis study was conducted on Lake Hamrin situated in Diyala governorate, focal Iraq, between latitudes 44º 53ʹ 26.16 '- 45º 07 ʹ 28.03ʺ and 34º 04ʹ 24.75ʺ ــ 34º 19ʹ 12.74ʺ . As in this study, the surface area of Hamrin Lake was calculated from satellite images during the period from October 2019 to September 2020, with an average satellite image for each month, furthermore,by utilizing the Normalized Differences Water Index (NDWI), the largest surface area was 264,617 km2 for October and the lowest surface area 140.202 km2 for September. The surface temperature of the lake water was also calculated from satellite images of the Landsat 8 satellite, based on ban
... Show MoreThe necessary optimality conditions with Lagrange multipliers are studied and derived for a new class that includes the system of Caputo–Katugampola fractional derivatives to the optimal control problems with considering the end time free. The formula for the integral by parts has been proven for the left Caputo–Katugampola fractional derivative that contributes to the finding and deriving the necessary optimality conditions. Also, three special cases are obtained, including the study of the necessary optimality conditions when both the final time and the final state are fixed. According to convexity assumptions prove that necessary optimality conditions are sufficient optimality conditions.
... Show MoreA sensitive, accurate, and affordable colorimetric method was developed for assaying prednisolone (PRZ) in various medicinal forms. The procedure involves the oxidation of PRZ by ferric ions, followed by complexation of the resulting ferrous ions with ferricyanide to produce a greenish-blue product. Common complexation conditions were thoroughly investigated. The mole ratio of FeCl₃·6H₂O to K₃Fe(CN)₆ was 8:1. The proposed mechanism of complexation was suggested and considered. Various parameters were optimized, including the reduction of the colorimetric reaction temperature to 50°C and the duration of heating and analysis to 20-30 minutes. The calibration curve was linear over the range of 1-60 µg/mL. The limit of detection (LOD
... Show MoreThis study conduct in Al-Muthanna governorate to assess five concentrations of
This paper displays a survey about the laboratory routine core analysis study on ten sandstone core samples taken from Zubair Reservoir/West Quarna Oil Field. The Petrophysical properties of rock as porosity, permeability, grain's size, roundness and sorting, type of mineral and volumes of shales inside the samples were tested by many apparatus in the Petroleum Technology Department/ University of Technology such as OFITE BLP-530 Gas Porosimeter, PERG-200TM Gas Permeameter and liquid Permeameter, GeoSpec2 apparatus (NMR method), Scanning Electron Microscopy (SEM) and OFITE Spectral Gamma Ray Logger apparatus. By comparing all the results of porosity and permeability measured by these instruments, it is clear a significant vari
... Show MoreTransference numbers of the aqueous zinc chloride and zinc sulphate solutions have been measured for the concentrations 0.03, 0.05, 0.07, 0.09 and 0.1 mol.dm-3at 298.15K, by using the modified Hittorf method. The dependence of transference number on concentration of each electrolyte was also investigated in an attempt to explain the value of the limiting transference number. The Longsworth method has been used for the extrapolation of zinc transference number in aqueous solutions, using the values of the limiting transference numbers of the appropriate values of the limiting equivalent conductance, it was possible to determine the corresponding values of the limiting ion conductance for the cations and anions of the electrolytes. The
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