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Improvements to the quality of underground water by introducing carbon dioxide
Mojca Poberžnik, Ludvik Trauner, Albrecht Leis, Aleksandra Lobnik, 2008, original scientific article

Abstract: The presented research work is focused on the development of an innovative way of economically improving the quality of underground water by the application of carbon dioxide. The basic pilot plant was developed with the idea of applying carbon dioxide in order to maintain the carbonate equilibria in water, pumped from under the ground. The optimal content of this natural component in underground water, used in urban areas for different purposes (e.g. drinking water, heating systems etc), simultaneously prevents corrosion and precipitated mineral deposits. The adaptation of an existing pilot plant started with operational testing and preliminary measurements. An appropriate sensor system for the online monitoring of the tap waterćs heating process measuring parameters such as the temperature, the concentration of dissolved carbon dioxide, the conductivity and the pH value was built in. Different amounts of carbon dioxide were applied during the two experimental stages. The composition of the water was regularly analysed using automatic titration and ionic chromatography. The gas-dosing control in the first phase was volumetric. Due to an observed inaccuracy in the gasdosing system, the volumetric dosing control was replaced with a system for the mass control of the introduced gas. Closing the system was considered to be suitable, as the water composition remained almost constant during the entire experiment. Improvements to the gas-dosing control and the closing of the system were carried out in the final phase of the pilot plant's adaptation. Further measurements were made in different seasons to test the seasonal influences on underground water's composition and the efficiency of the carbon dioxide supply.
Keywords: underground water, drinking water quality, pilot plant, carbonate equilibria, carbon dioxide, precipitation, scale
Published: 05.06.2018; Views: 566; Downloads: 41
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The magnetic and colloidal properties of $CoFe_2O_4$ nanoparticles synthesized by co-precipitation
Sašo Gyergyek, Mihael Drofenik, Darko Makovec, 2014, original scientific article

Abstract: Magnetic $CoFe_2O_4$ nanoparticles were synthesized by co-precipitation at 80 °C. This co-precipitation was achieved by the rapid addition of a strong base to an aqueous solution of cations. The investigation of the samples that were quenched at different times after the addition of the base, using transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDXS) and X-ray powder diffractometry, revealed the formation of a Co-deficient amorphous phase and $Co(OH)_2$, which rapidly reacted to form small $CoFe_2O_4$ nanoparticles. The nanoparticles grew with the time of aging at elevated temperature. The colloidal suspensions of the nanoparticles were prepared in both an aqueous medium and in a non-polar organic medium, with the adsorption of citric acid and ricinoleic acid on the nanoparticles, respectively. The measurements of the room-temperature magnetization revealed the ferrimagnetic state of the $CoFe_2O_4$ nanoparticles, while their suspensions displayed superparamagnetic behaviour.
Keywords: cobalt ferrite, nanoparticles, co-precipitation, colloidal suspensions, magnetic properties
Published: 30.08.2017; Views: 1874; Downloads: 58
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Synthesis and characterization of hardened Cu-Fe-Ni-P alloy
Goran Brovč, Goran Dražić, Blaž Karpe, Igor Đorđević, Gorazd Lojen, Borut Kosec, Milan Bizjak, 2015, original scientific article

Abstract: In the manufacturing industry of electrical contacts, the prohibition of the use of toxic metals (Cd, Be), and desire to avoid the alloying with precious metals (Ag) has created a need for new alloys with good electrical conductivity and high mechanical properties at elevated temperatures. As a potentially useful material for this purpose, we have analyzed the continuously cast Cu-Fe-Ni-P alloy in various heat treatment conditions. Sequence of phase transformations during heat treatment was followed by 4 point D.C. electrical resistivity measuring method, and analyzed by scanning (SEM) and transmission (TEM) electron microscopy. Measurements of Vickers hardness and electrical conductivity after various heat treatment procedures indicate on high potential of Cu-Fe-Ni-P alloys as a material for electrical contacts.
Keywords: copper alloys, precipitation hardening, electrical contacts, electrical conductivity
Published: 03.07.2017; Views: 1564; Downloads: 73
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Variability of seasonal and annual precipitation in Slovenia and its correlation with large-scale atmospheric circulation
Dragan Milošević, Stevan Savić, Milana Pantelić, Uglješa Stankov, Igor Žiberna, Dragan Dolinaj, Igor Leščešen, 2016, original scientific article

Abstract: This paper examines temporal and spatial variability and trends of annual and seasonal precipitation in Slovenia and their relationship with three atmospheric circulation patterns represented by their indices: North Atlantic Oscillation index (NAOi), Mediterranean Oscillation index (MOi) and Western Mediterranean Oscillation index (WeMOi). Data from 45 precipitation stations were used for the period 1963-2012. Mean annual precipitation varies from 736 mm in eastern Slovenia to 2,518 mm in northwestern Slovenia. A significant annual precipitation decrease (from -3% to -6% per decade) is observed in western Slovenia. Significant negative trends are observed in southwestern Slovenia in summer (from -4% to -10% per decade) and near the Adriatic coast in spring (from -6% to -10% per decade). Non-significant negative and positive trends are observed in winter and autumn, respectively. Results indicate significant correlations between winter precipitation and MOi (from -0.3 to -0.7), NAOi (from -0.3 to -0.6) and WeMOi (from 0.3 to 0.6). Significant WeMOi influence is observed in spring and autumn, while NAOi and MOi influence has not been detected. Annual precipitation and WeMOi are significantly correlated in central and eastern Slovenia, while significant NAOi and MOi influence is observed in western Slovenia (with the larger area covered by MOi influence).
Keywords: precipitation, atmospheric circulation, Europe, Slovenia
Published: 03.04.2017; Views: 582; Downloads: 359
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