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Open access

J. Csapó, G. Holló, I. Holló, R. V. Salamon, Sz. Salamon, Sz. Toró and Zs. Csapóné Kiss

Abstract

Until the middle of the last century, selenium was considered to be toxic, but recently it turned out to be a micronutrient with important physiological effects, whose lack impedes the functioning of several enzymes, while in the case of a prolonged deficiency, disease processes can also occur in the body. Hungary belongs to the selenium-deficient regions in Europe; therefore, our aim was to contribute to the improvement of selenium supply of the population through increasing the selenium content of milk and dairy products. A daily supplementation of 1-6 mg organic selenium to the feed of dairy cows increases the selenium content of milk from the value of 18 μg/kg to 94 μg/kg in 8 weeks, decreasing again to the initial value in 6 weeks after stopping the supplementation.

After producing various products from the control milk (18 μg/kg selenium content) and the selenium-enriched milk (53 μg/kg) obtained from dairy cattle fed on a feed supplemented with 2 mg selenium/day, we concluded that the selenium content of selenium-enriched milk compared to the products produced from the control milk increased from the value of 18.6 to 58.5 μg/kg in the case of yogurt, from 66.0 to 138.1 μg/kg in the case of telemea, from 80.8 to 163.7 μg/kg in the case of orda (urdă) and from 88.6 to 200.0 μg/kg in the case of semi-hard cheese obtained by mixed-coagulation. The selenium content of whey also increased significantly (from 8.8-9.7 μg/kg to 20.1-25.8 μg/kg), which could also be used as a food for people or feed for animals. According to our calculations, the selenium requirements of the developing organism could be satisfied by the consumption of 2-3 dl selenium-enriched milk until the age of 8 and with 4-6 dl selenium-enriched milk until the age of 20.

Open access

J. Wieczorek, B. Oleksiak, J. Łabaj, B. Węcki and M. Mańka

properties and a wear model of aluminium matrix composites - SiC particles designed for metal forming, Archives of Metallurgy and Materials 60 (1), 111-115 (2015). [12] V.I. Rigou, G. Marginean, D. Frunzaverde, C. V. Campian, Silver based composite coatings with improved sliding wear behavior, Wear 290-291, 61-65 (2012). [13] M. Dyzia, A. J. Dolata, J. Śleziona, Preliminary analysis of aluminum matrix compositions for composites reinforcement with carbon fibers, Steel Research International 83 (10), 981-987 (2012). [14] A

Open access

Szymon Piasecki, Robert Szmurlo and Marek Jasinski

Aachen University, Germany, pgs. 247, June 2010. [3] G. Wrona, M. Jasinski, "AC-DC Converter with Asymmetrical Higher Harmonics Compensation Function in Sustainable AC Grid", Versita, Transaction of Electrical, Control and Communication Engineering, No 2013/2, p. 5- 13 [4] T. Friedli, “Comparative Evaluation of Three-Phase Si and SiC AC-AC Converter Systems,” PhD Thesis, ETH Zurich University, Switzerland, pgs. 420, 2010. [5] J. Rabkowski, D. Peftitsis, H.P. Nee, “SiC power transistors - a new era in power electronics is

Open access

P. Chabera, A. Boczkowska, A. Morka, P. Kędzierski, T. Niezgoda, A. Oziębło and A. Witek

), 471-474 (2011). [13] B.A. Cheeseman and T.A. Bogetti, “Ballistic impact into fabric and compliant composite laminates”, Compos Struct. 61, 161-173 (2003). [14] E. Medvedovski, “Ballistic performance of armour ceramics: Influence of design and structure. Part 2”, Ceram. Int. 36 (1), 2117-2127 (2010). [15] A. Oziębło, P. Chabera, K. Perkowski, M. Osuchowski, I. Witosławska, A. Boczkowska, and A. Witek, “Effect of isostatic sintering on selected microstructural and mechanical properties of Al2O3 i SiC ceramics”, Ceramic

Open access

A. J. Dolata, M. Dyzia, L. Jaworska and P. Putyra

Abstract

The main purpose of the investigations was to develop the phase composition of the composite assuming that the component selection criterion will be the formability of piston work surfaces during the machining. Wear resistance under the friction conditions was assumed as the additional parameter for the assessment of composite material. In the study were used AlSi7Mg/SiC+Cg and AlSi7Mg/SiC+GR hybrid composites prepared by the stir casting method.

Open access

Qun Li and Ding Xu

Abstract

This paper considers a fading cognitive multiple access channel (CMAC), where multiple secondary users (SUs), who share the spectrum with a primary user (PU), transmit to a cognitive base station (CBS). A power station is assumed to harvest energy from the nature and then provide power to the SUs. We investigate the power allocation problems for such a CMAC to maximize the SU sum rate under the interference power constraint, the sum transmit power constraint and the peak transmit power constraint of each individual SU. In particular, two scenarios are considered: with successive interference cancellation (SIC) and without SIC. For the first scenario, the optimal power allocation algorithm is derived. For the second scenario, a heuristic algorithm is proposed. We show that the proposed algorithm with SIC outperforms the algorithm without SIC in terms of the SU sum rate, while the algorithm without SIC outperforms the algorithm with SIC in terms of the number of admitted SUs for a high sum transmit power limit and a low peak transmit power limit of each individual SU.

Open access

M. Chmielewski, K. Pietrzak, A. Strojny-Nędza, D. Jarząbek and S. Nosewicz

Abstract

This paper analyses the technological aspects of the interface formation in the copper-silicon carbide composite and its effect on the material’s microstructure and properties. Cu-SiC composites with two different volume content of ceramic reinforcement were fabricated by hot pressing (HP) and spark plasma sintering (SPS) technique. In order to protect SiC surface from its decomposition, the powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. Microstructural analyses provided by scanning electron microscopy revealed the significant differences at metal-ceramic interface. Adhesion force and fracture strength of the interface between SiC particles and copper matrix were measured. Thermal conductivity of composites was determined using laser flash method. The obtained results are discussed with reference to changes in the area of metal-ceramic boundary.

Open access

E. Ābele

Recent advances in the fluoride ion-mediated reactions of silanes containing Si-H, Si-F, Si-C, Si-O, Si-N, Si-Sn bonds are described. Application of silicon bond activation by fluoride ion in the syntheses of different types of organic compounds has been discussed. The literature data published from January 2009 to December 2011 are discussed in this review.

Open access

M. Hebda, H. Dębecka, K. Miernik and J. Kazior

Abstract

The influence of adding different amounts of silicon carbide on the properties (density, transverse rupture strength, microhardness and corrosion resistance) and microstructure of low alloy steel was investigated. Samples were prepared by mechanical alloying (MA) process and sintered by spark plasma sintering (SPS) technique. After the SPS process, half of each of obtained samples was heat-treated in a vacuum furnace. The results show that the high-density materials have been achieved. Homogeneous and fine microstructure was obtained. The heat treatment that followed the SPS process resulted in an increase in the mechanical and plastic properties of samples with the addition 1wt. % of silicon carbide. The investigated compositions containing 1 wt.% of SiC had better corrosion resistance than samples with 3 wt.% of silicon carbide addition. Moreover, corrosion resistance of the samples with 1 wt.% of SiC can further be improved by applying heat treatment.

Open access

V. V. Malysheva, A.I. Gabb, D. B. Shakhnina, A. D. Pisanenkoa, M. Ambrovac, V. Danielikc and P. Fellnerc

Abstract

The systems suitable for a high-temperature electrochemical synthesis on the surfaces of diamond, boron nitride, and silicon and boron carbides were selected on the basis of thermodynamic analysis of the reactions of the dielectrics and semiconductors with ionic melts. The results obtained in the electrochemical study of these systems are reported. As example, the electrodeposition of molybdenum carbide on diamond, BN, SiC and boron carbide surfaces is discussed in detail.